Multistage gas generator for air bag and air bag apparatus

ABSTRACT

A multistage gas generator for an air bag has ignition devices  51  and  61  respectively disposed in the combustion chambers  50  and  60  provided in a housing  3 . A lead wire  9  for sending an ignition signal to each igniter  8  is provided with a connector  10 . The connector  10  is provided with a defining element  17  for specifying unique combination of connection between the respective ignition signal-outputting unit and the respective igniters  8.

This application is a divisional of application Ser. No. 09/601,238,filed on Sep. 25, 2000. application Ser. No. 09/601,238 is the nationalphase of PCT International Application No. PCT/JP00/00800 filed on Feb.15, 2000 under 35 U.S.C. §371. The entire contents of each of theabove-identified applications are hereby incorporated by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a multistage gas generator for an airbag and an air bag apparatus using the gas generator.

PRIOR ART

An air bag system which is mounted on various kinds of vehicles and thelike including automobiles, aims to hold an occupant by means of an airbag (a bag body) rapidly inflated by a gas when the vehicle collides ata high speed so as to prevent the occupant from crashing into a hardportion inside the vehicle such as a steering wheel, a windscreen due toan inertia and being injured. This kind of air bag system generallycomprises a gas generator to be actuated according to a collision of thevehicle and discharge a gas, and an air bag to introduce the gas toinflate.

It is desired that the air bag system of this type can safely restrainthe occupant even when frame of the occupant (for example, whether asitting height is long or short, whether an adult or a child, and thelike), a sitting attitude (for example, an attitude of holding on thesteering wheel) and the like are different. Then, there has beenconventionally suggested an air bag system which actuates, applying animpact to the occupant as small as possible at the initial stage of theactuation. Gas generators in such a system are disclosed in JP-A8-207696, U.S. Pat. Nos. 4,998,751 and 4,950,458. JP-A 8-207696 suggestsa gas generator in which one igniter ignites two kinds of gas generatingagent capsules so as to generate the gas at two stages. U.S. Pat. Nos.4,998,751 and 4,950,458 suggest a gas generator in which two combustionchambers are provided for controlling actuation of the gas generator soas to generate the gas at two stages due to a expanded flame of the gasgenerating agent.

Further, in JP-A 9-183359, and DE-B 19620758, there is disclosed a gasgenerator in which two combustion chambers storing a gas generatingagent are provided in a housing and an igniter is arranged in eachcombustion chamber, so as to adjust an activation timing of each of theigniters, thereby adjusting an output of the gas generator.

However, these above conventional gas generators are not a multistagegas generator for an air bag with a simple structure which can bemanufactured easily, suppressing the entire size of the container(housing).

DISCLOSURE OF THE INVENTION

The present invention provides a multistage gas generator for an airbag, wherein, at the initial stage of actuation, the gas generator isactuated to give a passenger as a small impact as possible, andaccording to variation of passengers' physiques (such that a sittingheight is tall or low, adult or child) and sitting postures (such asclinging to a steering wheel), actuation output of the gas generator andtiming of increase of output can be arbitrarily adjusted in order torestrain the passenger safely, and the gas generator can be manufacturedeasily with a simple structure, the entire size of the container(housing) can be suppressed, and finally the volume ratio of eachcombustion chamber can be arbitrarily be adjusted.

The present invention is characterized in an inner structure, speciallya layout structure of the combustion chambers capable of suppressing theentire size of the gas generator and adjusting the volume ratio of eachof the combustion chambers arbitrarily in a multistage gas generator foran air bag provided with a plural combustion chambers inside the housingthereof.

In other words, the multistage gas generator of the present inventionhaving a cylindrical housing comprising a diffuser shell with aplurality of gas discharge ports formed in a cylindrical side wall and aclosure shell forming a inner space with the diffuser shell, a pluralityof combustion chambers for accommodating gas generating means providedin a cylindrical housing, and ignition means disposed in the respectivecombustion chambers to ignite and burn the gas generating means,wherein, in the housing, at least one of the combustion chambers isdisposed in the inner side of an inner shell provided eccentrically withrespect to a center axis of the housing, the ignition means provided forthe respective combustion chambers are disposed eccentrically withrespect to the center axis of the housing.

Further, in the gas generator of the present invention, a communicationhole which allows mutual communication between the combustion chamberscan be provided.

An automatic ignition material (AIM) which is to be ignited and burnt bytransmitted heat may be disposed in either one of the combustionchambers.

The present invention further provides a multistage air bag apparatuswhich comprises the above-described gas generator, an ignitionsignal-outputting means provided with as many outputting portions, whichoutputs activation signals to the igniters on impact, as the igniters ofthe ignition means, and a plurality of lead wires having connectors, theigniters and the outputting portions are connected to each other throughthe lead wires having the connectors, and the connectors includedefining means for deciding the unique connection between one of theconnectors and one of the outputting portions.

The above gas generator may further comprise a cylindrical filter meansfor purifying and/or cooling an activation gas, one or both of axial endsurfaces of the filter means may be formed as inclining end surfaceswhich get narrower in the axial extending direction and the interiorangle with respect to the inner peripheral surface is an acute angle,and a supporting portion which is opposed to the inclining end surfaceof the filter may be provided in the housing (a self-contracting typefilter).

In the present invention, most of an outer surface of the inner shellcan be in direct contact with gas generating agent existing outside ofthe inner shell without interposing a heat insulator. The gas generatingagent comes into contact with the outer surface of the inner shell wherethe communication hole is provided. A wall of the inner shell existsbetween a first gas generating agent which burns first and the othersecond gas generating agent. Even if the first gas generating burns, thesecond gas generating agent will never start burning before actuation ofa second igniter, and the second gas generating agent is burnt byactuation of the second igniter before a temperature of the second gasgenerating agent reaches an ignition temperature by heat transfer.

After the first gas generating is ignited, if the gas generator is leftstanding without igniting the second gas generating agent, the secondgas generating agent is ignited after about 10 seconds.

In the present invention, it is generally preferable that the innershell is of cylindrical shape whose upper end is closed and itshorizontal cross sectional shape is circular. The horizontal crosssectional shape of the inner shell may be formed into various shapessuch as rectangular shape and elliptic shape. However, it is desirableto form the horizontal cross sectional shape of the inner shell intocircular in view of easiness of connection. The inner shell is disposedin the housing eccentrically with respect to the center axis of thehousing. That is, the inner shell is disposed in the housing such that acenter of the inner shell does not coincide with a center of thehousing, and the inner shell is disposed in the housing eccentricallywith respect to the cylindrical housing. Therefore, even if the planeshape of the housing is substantially elliptic, in case that the centerof the plane shape and the center of the inner shell are deviated fromeach other, the inner shell and the housing are deviated from eachother. Besides, the center axis of the housing is specified exclusivelybased on the plane shape of the cylindrical body, and even if thehousing has a flange for mounting the housing to the module, the flangeis not taken into consideration when the center axis of the housing isspecified.

The ignition means disposed in the respective combustion chambersinclude an igniter which is actuated by electric signal. The igniterscan be provided aligned in the axial direction of the housing. Theclosure shell constituting the housing can include a collar portion forfixing the igniter, and the igniter can be fixed to the collar portion.In this case, it is preferable that all igniters included in therespective ignition means are fixed to a single collar portion. This isbecause when the closure shell is formed including the collar portion,by fixing the plurality of igniters to the collar portion beforehand,the plurality of igniters can be fixed in the housing with a singleoperation for forming the closure shell, which is advantageous inmanufacture.

The inner shell disposed in the housing eccentrically is of cylindricalshape and the inner shell includes an opening portion which opens bycombustion of the gas generating means in one of the combustionchambers. The inner shell can be formed into another shape as describedabove. However, in view of easiness in connecting to the closure shell,it is preferable that the plane cross sectional shape is circle. Theinner shell enable the gas to flow through the combustion chambers whichare defined inside and outside of the inner shell by opening the openingportion. Such opening portion may be formed by forming a plurality ofholes in the peripheral wall of the inner shell, and by closing theholes using breaking members. The holes closed by the breaking memberscan be opened exclusively by burning the gas generating means in thecombustion chambers provided inside the inner shell. The hole is openedby combustion of the gas generating means, e.g., by rupturing, peeling,burning or detaching the breaking member due to a pressure caused bycombustion of the gas generating means. Alternatively, this can berealized by providing the inner shell with a notch or by reducing thethickness of a portion of the inner shell. A shielding plate can bedisposed outside of the opening portion, and the shielding plate canprevent flame generated in the combustion chamber provided outside theinner shell from coming into direct contact with the opening portion.The opening portion may be formed such as to be opened only bycombustion of the gas generating means in one of the combustionchambers.

As described above, the inner shell is disposed in the housingeccentrically with respect to the center axis of the housing, and theignition means disposed in each of the combustion chambers is disposedeccentrically with respect to the center axis of the housing. With thisstructure, it is possible to suppress the size of the housing to theminimum, and flexibility in volume, layout and the like of thecombustion chamber can be maximized. That is, when two combustionchambers are defined in the housing, by disposing the inner shelleccentrically in the housing and defining a first combustion chamber onthe outer side thereof and defining a second combustion chamber on theinner side, the volume ratio of the first and second combustion chamberscan be freely changed by changing the volume of the inner shell. At thattime, if the igniter of the ignition means disposed in each of thecombustion chambers is also disposed eccentrically with respect to thecenter axis of the housing, the igniter disposed in the first combustionchamber will not be an obstacle to increase the volume of the secondcombustion chamber. Therefore, in the present invention, it is possibleto maximize the flexibility in volume and the like of the first andsecond combustion chambers.

Further, the present invention provides a multistage gas generator foran air bag which is provided, in the combustion chamber inside the innershell, with an automatic ignition material (AIM), to be ignited andburnt by heat generated by combustion of the gas generating meansdisposed in the combustion chamber outside the inner shell, and alsoprovides a multistage gas generator for an air bag in which theautomatic ignition material (AIM) is included in the ignition meansdisposed in the combustion chamber inside the inner shell. That is, inmost cases, when the multistage type gas generator is actuated, all theignition means are actuated and the gas generating means in all thecombustion chambers are burnt. However, under a certain actuatingcondition, there is a case in which only one of the ignition means isactuated intentionally to burn the gas generating means in a selectedcombustion chamber. In this case, remaining ignition means and gasgenerating means which were not actuated cause inconvenience at the timeof later disposal or damping. Therefore, it is preferable to ignite andburn them after actuation of the gas generator. Thereupon, by disposingthe automatic ignition material (AIM) in the combustion chamber and/orignition means, even when the gas generating means and/or ignition meansin either of the combustion chambers were not burnt and remained, it ispossible to ignite and burn the gas generating and/or ignition means ata delayed timing by heat (transmitted heat) caused by combustion of thegas generating means in the other combustion chamber. Therefore, in thepresent invention also, in the combustion chamber and/or the ignitionmeans provided inside the inner shell, it is preferable to dispose theautomatic ignition material (AIM) which is to be ignited and burnt byheat generated by combustion of the gas generating means in thecombustion chamber provided outside the inner shell. As the automaticignition material (AIM), material which is ignited with a lowertemperature compared with the gas generating means or transfer charge ispreferably used. The gas generating means is ignited by the automaticignition material (AIM) after activation of the gas generating means.That is, the ignition of the gas generating means by the automaticignition material is different from the ignition of the gas generatingagent delaying intentionally the actuation timing of the ignition meansfor the purpose of adjusting the actuation performance of the gasgenerator. The ignition by AIM is performed when a sufficient period oftime has passed after actuations at intentional intervals of theigniters to adjust the actuation performance of the gas generator.Therefore, after one ignition means is actuated first, the remaining gasgenerating means will not be ignited by the automatic ignition materialbefore the other ignition means is actuated with intentionally delayedtiming.

The housing can be formed by joining the diffuser shell and the closureshell by various welding methods such as friction welding, electron beamwelding, laser welding, TIG welding and projection welding. Among thesewelding methods, when both the shells are joined by friction welding toform the housing, it is preferable to carry out the friction weldingwhile fixing the closure shell. Generally, both the shells are joined atthe final stage. And by performing the friction welding while fixing theclosure shell in this manner, even when the center of gravity of theclosure shell side is deviated such that the ignition means is disposedeccentrically, both the shells can be stably be joined. In other words,the friction welding is carried out in a state where one object is fixedand the other object is rotated. If the center of gravity of the objectto be rotated is deviated, it is difficult to stably carry out thefriction welding. Thereupon, in the present invention, stable frictionwelding is realized by carrying out the friction welding while fixingthe closure shell side.

When the friction welding is carried out while fixing the closure shell,it is preferable that the flange portion for mounting the gas generatorto the module case is provided on the closure shell, and the flangeportion is formed with a positioning portion for specifying a directionand/or a position of the closure shell which is fixed at the time offriction welding. When the flange portion has a plurality radiallyprojections for fixing the gas generator to the module case, thepositioning portion is realized by forming the projectionsasymmetrically with respect to each other. Only one projecting isprovided, the projection itself can be the positioning portion. Byforming the flange portion with the positioning portion in this manner,when the inner shell is fixed in the housing by the friction welding,the joining position of the housing is always determined constantly withrespect to the inner shell which is rotated. Therefore, it is possibleto reliably fix the inner shell in a predetermined direction and/orposition. By forming the positioning portion on the flange portion, theflange portion is used both for positioning and mounting of the gasgenerator. In the present invention, in order to fix the closure shellin the predetermined direction and/or a position at the time of frictionwelding, it is of course possible to form the positioning portion onanother portion such as a peripheral wall and bottom surface instead ofthe flange.

Further, the igniting means disposed in the combustion chamber caninclude injecting-direction restricting means for restricting aninjecting direction of flame which is generated by the actuation of theignition means. The injecting-direction restricting means is used forrestricting the injecting direction of flame generated by actuation ofthe ignition means, i.e., the injecting direction of flame to ignite andburn the gas generating means.

The injecting-direction restricting means can envelop at least a portionof the ignition means which generates the flame, and includes a hollowcontainer having two or more flame-transferring holes for restrictingthe injecting direction of the flame into a desired direction. Examplesof such injecting-direction restricting means are deflector plates, acylindrical member capable of enveloping the entire ignition means, anda cup-like container or the like capable of enveloping a portion of theignition means where the flame is generated.

By using such injecting-direction restricting means, it is possible torestrict the injecting direction of flame of the ignition means to adirection along the inner wall surface of the combustion chamber. The“direction along the inner wall surface of the combustion chamber” meansthat the flame is ejected, moving in a direction which coincides with ashape of the inner wall surface. By restricting the injecting directionof the flame of the ignition means in this manner, it is possible topreferably burn the gas generating means in the combustion chamber evenwhen the ignition means is not disposed at center of the combustionchamber or when the combustion chamber is not circular in shape and adistance between the gas generating means and the ignition meansdisposed at corners of the combustion chamber is remarkably fair.

As the injecting-direction restricting means, the gas discharge portsmay be distributed so that the number of the gas discharge ports formedfurther from the first igniter may be greater or the total opening areathereof may be greater than otherwise. It is preferable to combine theseto form the injecting-direction restricting means.

The outputs of the ignition means disposed in the respective combustionchambers can be changed from one another. When the ignition meansinclude a transfer charge in addition to the igniters having differentoutputs, it is possible to adjust the material, shape or amount of thetransfer charge, thereby adjusting the output of the ignition means.

A retainer can be disposed inside the inner shell in order to performthe connection with the closure shell stably and smoothly. The retainermay be a gas generating agent fixing member shown in the embodiment.When fixing the inner shell to the closure shell by friction welding,crimping, resistance welding, convex-concave joint or the like, theretainer keeps the gas generating agent in the inner shell so that thegas generating agent does not come into direct contact with the closureshell, and also obtains a space for accommodating the ignition means inthe inner shell. By using this retainer, the assembling operation can befacilitated. Especially when charging directions of two or more gasgenerating means are different at the time of assembling as in thepresent invention, it is effective to use the retainer. The retainer mayhave a canister-like shape made of aluminum or iron, or may be a porousmaterial made of wire mesh or the like.

The igniter included in the ignition means is activated upon receptionof activation signal of the gas generator which is outputted from acontrol unit or the like. Therefore, a cable for transmitting theactivation signal from the control unit or the like is connected to eachof the igniters. Since the gas generator of the present inventionincludes two or more ignition means, two or more igniters are included.By pulling out the cables connected to the igniters in the samedirection, the gas generator can be mounted to the module easilyafterwards.

In the multistage gas generator for the air bag of the presentinvention, when the ignition means disposed in each of the combustionchambers comprises an igniter which is to be activated by an electricsignal and a cable for transmitting the electric signal is connected toeach igniter through a connector, it is preferable that the connectorhas a positioning means capable of connecting the cable to only one ofthe igniters. That is, in the cables which are connected to therespective igniters to transmit different activation signals with theaim of adjusting activation timing, if a wrong cable is connected to oneof the igniters, a desired activation output can never be obtained.Thereupon, the respective igniters are provided with the respectivepositioning means to be connected to exclusively one of the cables,which can prevent the connection error. Such positioning means can berealized by forming the engaging portions, which is between the igniterand the connector and for connecting the igniter and the cable, intodifferent shapes for the respective igniters, or by forming theconnectors with groove and/or projections having different positionsand/or shapes. Additionally, plural cables of the respective igniterscan be collected to one connector and the connector can be formed withthe positioning means. The positioning means provided in the connectorof the invention also includes all cases in which any elementsdetermining whether a plug and a jack can be connected such as a case inwhich shape and size of a portion (blade or current-carrying plug) whichconnects and energize the connector) or shape and size of the case ofthe connector are different. That is, any means which uniquely definescombination of connection between the cable and the ignition isincluded.

With a gas generator comprising a housing having a plurality ofcombustion chambers therein and gas generating means which are differentfrom each other in an amount of a generated gas per unit time in therespective combustion chambers such as gas generating means which aredifferent from each other in at least one of burning rate, composition,composition ratio, shape and amount, activation performance of the gasgenerator, particularly the change with time of the gas dischargingamount can be adjusted distinctively and arbitrarily. When the gasgenerating means in each of the combustion chambers is independentlyignited and burnt with arbitrary timing, ignition means which isindependently ignited and burnt is disposed in each of the combustionchambers. As the gas generating means, it is possible to use inorganicazide which is conventionally and widely used such as azide-based gasgenerating agent based on sodium azide or non-azide-based gas generatingagent not based on inorganic azide. If safety is taken intoconsideration, non-azide-based gas generating agent is desirable. Thegas generating means is appropriately selected in accordance withrequirements such as burning rate, non-toxicity, combustion temperature,decomposition-starting temperature. When gas generating means havingdifferent burning rate for each combustion chamber, it is possible touse gas generating means having different composition or compositionratio itself by using inorganic non-azide such as sodium azide,non-azide such as nitroguanidine or the like as fuel and nitrogensource, or gas generating means in which the shape of composition can bechanged such as pellet-like, wafer-like, hollow columnar, disk-like,body having a single hole, porous body or the surface area is changed bysize of the molded article. Especially when the gas generating means isformed into a porous body having a plurality of through-holes, althoughlayout of the holes is not limited, it is preferable to a distancebetween an outer end of the molded article and a center of the hole anda distance between the centers of the respective holes are substantiallyequal to each other so that performance of the gas generator isstabilized. More specifically, in a cylindrical molded article whosecross section is circular, a preferred structure is such that one holeis arranged at the center and six holes are formed around the hole sothat the center of each hole is the apex of regular triangles of theequal distances between the holes. Further, it is conceived to disposeone hole at a center and 18 holes around the central hole. The number ofholes and layout of the holes are determined based on combination ofeasiness of manufacture of the gas generating agent, manufacturing costand performance, and accordingly, the number of holes and layout of theholes are not limited.

In a gas generator (pyrotechnic gas generator) using solid gasgenerating means for obtaining gas for expanding the air bag, a filteror a coolant is usually preferably used for purifying or coolingcombustion gas generated by combustion of the gas generating means.Therefore, in the gas generator of the present invention, when acombustion gas generated by combustion of the gas generating means ispurified and/or cooled, filter means formed by compressing laminatedwire mesh can be used. If such filter means is formed intoself-contracting structure in which the filter means can be pushedradially outward by the pressure of the combustion gas and its upper andlower ends are pressed by the inner surface of the housing, a short passof the combustion gas between the end surface of the filter means andthe inner surface of the housing can be avoided without providing anyspecial member. Such a self-contracting structure can be realized byinclining upper and lower inner surfaces of the housing such as tonarrow the inner surfaces, and by inclining upper and lower end surfacesof the filter means such as to be aligned with the upper and lower innersurfaces of the housing. Inside and outside of the filter means can beformed into different laminated wire mesh bodies to provide a triplestructure, so that the inner side of the filter means can exhibitprotection function of the filter means and the outer side of the filtercan exhibit suppressing expansion function of the filter means. Thesuppressing expansion function can be exhibited by supporting an outerperiphery of the filter means with an outer layer made of laminated wiremesh body, porous cylindrical body, annular belt body or the like suchas to suppress the expansion.

When the plurality of combustion chambers are provided in the housingand combustion gas is generated by combustion of the gas generatingmeans in the respective combustion chambers as described above, it ispreferable that the combustion gas discharged from each combustionchamber passes through a common filter. If all combustion gas passesthrough the common filter means, it is enough to dispose one filtermeans in the housing and as a result, the entire volume can be reduced,and the manufacturing cost can be reduced. Further, the combustion gaspassing through the common filter means can be discharged from a commongas discharge port(s) formed in the housing.

The above-described gas generator for the air bag is accommodated in amodule case together with an air bag (bag) into which gas generated bythe gas generator is introduced for expansion, thereby constituting theair bag apparatus. In this air bag apparatus, the gas generator isactuated when an impact sensor senses an impact, thereby discharging thecombustion gas from the gas discharge port of the housing. Thecombustion gas flows into the air bag so that the air bag breaks amodule cover and expands, thereby forming a cushion between a passengerand a hard structural member of the vehicle for absorbing the impact.

According to the present invention, there is provided a multistage gasgenerator for an air bag in which the entire size of the container canbe suppressed, the structure is simple and the gas generator can bemanufactured easily, the gas generator is actuated, at the initial stageof actuation, to give a passenger as a small impact as possible, and,according to variation of passengers' physiques (such that a sittingheight is tall or low, adult or child) and sitting postures (such asclinging to a steering wheel), actuation output of the gas generator andtiming of increase of output can be arbitrarily adjusted in order torestrain the passenger safely.

Further in the gas generator of the invention, at least one of thecombustion chambers is disposed eccentrically with respect to thehousing, the ignition means provided for each of the combustion chambersis disposed in the housing eccentrically with respect to the housing.With this feature, it is possible to maximize the flexibility of thecombustion chamber while suppressing the size of the housing in itsradial direction.

The gas generator of the eccentric structure can be realized byincluding AIM, a connector, a self-contracting type filer which will beexplained later, or combination thereof. The gas generator can also berealized by combining other parts described in the presentspecification.

According to the present invention, the gas generator for the air bagincludes a plurality of igniters, activation signals are outputted fromthe ignition signal-outputting means to the igniters respectively,connection error between each igniter and the ignition signal outputtingapparatus outputting section is eliminated, and the multistage type gasgenerator can always actuate with desired output. Therefore, in themultistage type air bag apparatus capable of adjusting actuation outputand timing of output increase, desired actuation performance can alwaysbe obtained.

Further, also when the filter means radially expands by passage of theactivation gas, since the inclining end surface of the filter means isin contact with the supporting portion in the housing and the surfacecontact between both the members can be maintained, and thereby, shortpass of the activation gas can be effectively avoided. Since the filtermeans is a member capable of expanding, high assembling accuracy is notrequired, and assembling operation into the hosing can be easily carriedout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional view showing one embodiment of agas generator of the present invention;

FIG. 2 is a plan view of the embodiment;

FIGS. 3(a) and (b) are cross sectional views of the gas generator of theinvention;

FIG. 4 is a rear view of the gas generator of the invention;

FIGS. 5(a)-(d) are partial perspective views showing positioning means;

FIG. 6 is a partial cross sectional view showing a filter ofself-contracting structure;

FIG. 7 is a rear view of the gas generator showing a positioningportion;

FIG. 8 is a vertical cross sectional view showing another embodiment ofthe gas generator of the invention;

FIG. 9 is a view showing a structure of an air bag apparatus of theinvention;

FIG. 10 is a schematic vertical cross sectional view showing oneembodiment of the air bag apparatus of the invention;

FIG. 11 is a schematic perspective view showing another embodiment ofthe air bag apparatus;

FIGS. 12(a)-(d) are schematic perspective views showing an embodiment ofdefining means;

FIGS. 13(a)-(c) are schematic perspective views showing anotherembodiment of defining means;

FIG. 14 is a schematic perspective view showing another embodiment ofthe air bag apparatus;

FIG. 15 is a schematic perspective view showing still another embodimentof the air bag apparatus;

FIGS. 16(a)-(c) are schematic perspective views showing still anotherembodiment of defining means;

FIG. 17 is a schematic perspective view showing another embodiment ofthe air bag apparatus;

FIG. 18 is a vertical cross sectional view showing another embodiment ofthe gas generator of the present invention;

FIG. 19 is a vertical cross sectional view showing the embodiment of agas generator of the present invention;

FIG. 20 is a vertical cross sectional view showing an embodiment offilter means of the invention;

FIG. 21 is a vertical cross sectional view showing another embodiment ofthe filter means;

FIG. 22 is a vertical cross sectional view showing another embodiment ofthe gas generator;

FIG. 23 is a vertical cross sectional view showing still anotherembodiment of the gas generator;

FIG. 24 is a vertical cross sectional view showing another embodiment ofthe gas generator;

FIG. 25 is a vertical cross sectional view showing another embodiment ofthe gas generator;

FIG. 26 is a phantom view of the gas generator shown in FIG. 25;

FIG. 27 is a vertical cross sectional view showing another embodiment ofthe gas generator;

FIG. 28 is a vertical cross sectional view showing one embodiment of thegas generator of the invention;

FIG. 29 is a exploded perspective view of an essential portion showing apartition wall;

FIGS. 30(a)-(d) are exploded perspective views of an essential portionshowing the positioning means;

FIG. 31 is a vertical cross sectional view showing another embodiment ofthe gas generator for an air bag;

FIG. 32 is a vertical cross sectional view showing still anotherembodiment of the gas generator for the air bag; and

FIG. 33 is a phantom view of the gas generator shown in FIG. 31.

FIG. 34 is a plain view of the present embodiment having a deflectorplate.

EXPLANATION OF SYMBOLS

1 diffuser shell

2 closure shell

3 housing

4 inner shell

5 opening portion

8 transfer charge

10 gas discharge port

25 coolant/filter

32 flange

50 first combustion chamber

51 first igniter

52 first gas generating agent

60 second combustion chamber

61 second igniter

62 second gas generating agent

101 gas generator for air bag

102 activation signal outputting means

103 air bag

107 activation signal outputting portion

108 igniter

109 lead wire

110 connector

301 diffuser shell

302 closure shell

303 housing

305 filter means

309 gas generating agent

311 igniter

351 inclining end surface of filter means

352, 452, 552, 652, 752 inclining surface (supporting portion)

353 filter means supporting means

453, 553, 653, 753 inclining portion of housing

803 housing

822 coolant/filter

1105 a first combustion chamber

1105 b second combustion chamber

1107 partition wall

1109 a first gas generating agent

1109 b second gas generating agent

1112 a first igniter

1112 b second igniter

1113 initiator collar

1185 automatic ignition material (AIM)

BEST MODE FOR CARRYING OUT THE INVENTION

A multistage gas generator for an air bag of the present invention willbe explained below based on embodiments shown in the drawings.

Embodiment of Eccentric Structure

FIG. 1 is a vertical cross sectional view showing one embodiment of thegas generator of the present invention. The gas generator shown in FIG.1 has a structure suitable to be disposed on a driver side.

In FIG. 1, the gas generator includes a cylindrical. housing 3 which isformed by joining, using friction welding, a diffuser shell 1 having agas discharge port 10 and a closure shell 2 forming an interioraccommodating space with the diffuser shell. A capsule-like inner shell4 whose horizontal cross section is circular and upper end thereof isclosed is disposed and fixed in the housing 3 eccentrically with respectto a center axis of the housing. An eccentric degree of the inner shellwith respect to the housing can be appropriately changed in accordancewith a desired volume ratio of the combustion chambers. The eccentricdegree might be changed depending upon a structure inside the housing,e.g., whether or not there exists a coolant/filter 25. For example, whenthe coolant/filter 25 is placed such as to be opposed to a peripheralwall surface as in the gas generator shown in FIG. 1, the eccentricdegree can be appropriately selected within a range of 10 to 75%.However, since this numeral range might be changed depending upon a sizeof the igniter and the like, the numeric value range is shown as anindex of eccentricity of the inner shell 4 in the gas generator shown inFIG. 1.

The horizontal cross sectional shape of the inner shell can be formedinto various shapes such as rectangular shape and elliptic shape. Inview of facilitating joint to the closure shell 2 and the like, thehorizontal cross sectional shape of the inner shell is preferably formedinto circular. In other words, the horizontal plane cross sectionalshape of the inner shell 4 needs to be circular, when the inner shell 4is joined to the closure shell 2 by the friction welding. Further, whenthese members are joined by laser welding, it is necessary to keep thelaser irradiation distance constant.

The inner shell 4 is disposed while securing a slight gap between theinner shell 4 and the coolant/filter 25. This gap is secured to form agas flow between the coolant/filter 25 and the inner shell 4 and toeffectively use the entire surface of the filter 25. And when an openingportion of the inner shell 4 is opened as will be described later, thecoolant/filter 25 will not hinder because of the gap. Therefore, thisgap is appropriately selected in a range of the above purpose.

The inner shell 4 defines a first combustion chamber 50 and a secondcombustion chamber 60. That is, the first combustion chamber 50 isprovided outside the inner shell, and the second combustion chamber 60is provided inside the inner shell 4. A volume ratio of the firstcombustion chamber 50 and the second combustion chamber 60 (a volume ofthe first combustion chamber: a volume of the second combustion chamber)is set to 3.3:1 in the present embodiment, but this ratio can beappropriately selected within a rage of 97:1 to 1:1. This volume ratioalso might be changed depending upon a size of the igniter, a shape ofthe gas generating agent and the like. Therefore, the numeric valuerange is shown as a range which can be selected in the structure of thegas generator shown in FIG. 1.

Gas generating agent (52, 62) are respectively accommodated in thesecond combustion chamber 60 and the first combustion chamber 50 whichare isolated form each other by the inner shell 4. The first gasgenerating agent 52 is accommodated in the first combustion chamber 50,and the second gas generating agent 62 is accommodated in the secondcombustion chamber 60. In the present embodiment, the first gasgenerating agent 52 and the second gas generating agent 62 are the samein shape and the like, the respective combustion chambers canaccommodate gas generating means which are different from each other inat least one of burning rate, composition, composition ratio and amount.

The inner shell 4 defining the first combustion chamber 50 and thesecond combustion chamber 60 is disposed eccentrically with respect tothe center axis of the housing 3. The second combustion chamber 60provided inside the inner shell 4 is also eccentric with respect to thehousing 3. Igniters are respectively disposed in the first combustionchamber 50 and the second combustion chamber 60, and among them, thesecond igniter 61 disposed in the second combustion chamber is disposedat a center of the second combustion chamber 60 which is eccentric withrespect to the center axis of the housing 3. As a result, flamegenerated due to the actuation of the igniter 61 can uniformly burn thesecond gas generating agent 62. Further, the second igniter 61 and thefirst igniter 51 which is disposed in the first combustion chamber 50are both disposed eccentrically with respect to the center axis of thehousing 3. By disposing the first and second igniters as well as theinner shell eccentrically with respect to the center axis of the housing3, variation in volume ratio of the first and second combustion chamberscan be expanded, and a size of the housing 3 in its radial direction canbe suppressed to the minimum.

Among the igniters disposed in the respective combustion chambers, theigniter 51 disposed in the first combustion chamber 50 has transfercharge 8 around and above the igniter 51. The transfer charge 8 isaccommodated in a transfer charge container 26 in order to facilitateassembly of the gas generator, and to prevent the transfer charge 8 frombeing dispersed in the first combustion chamber 50 due to impacts orvibrations caused while the transfer charge is mounted in a vehicle sothat the ignition performance with respect to the first gas generatingagent 52 is deteriorated. The transfer charge container 26 is made ofaluminum having such a thickness (e.g., about 200 μm) that the container26 is easily broken by combustion of the transfer charge 8 in thetransfer charge container 26 to transfer flame to its surroundings. Atransfer charge such as that disposed in the first combustion chamber 50is not necessarily needed for the second combustion chamber 60. This isbecause the second gas generating agent 62 is ignited more easily, thanthe first gas generating agent 52, and the pressure of the secondcombustion chamber is increasing in a sealed state until the breakingmember 7 for sealing a hole 6 of the below-described inner shell 4 isruptured. The breaking member 7 is not ruptured even when the internalpressure of the first combustion chamber 50 increases due to thecombustion of the first gas generating agent 52 but it is ruptured whenthe internal pressure of the second combustion chamber 60 increases morethan that of the first combustion chamber 50. However, the transfercharge can be used as required.

A cylindrical member 36 is disposed in the first combustion chamber 50so as to surround the first igniter 51 and a radially outer side of thetransfer charge 8 disposed above the first igniter 51. The cylindricalmember 36 is formed into a cylindrical shape whose upper and lower endsare opened, one end thereof is fitted over an outer periphery of aportion to which the igniter 51 is fixed without gap, and the other endis interposed by the retainer 11 provided in the vicinity of an innersurface of a ceiling portion of the diffuser shell 1 and fixed to apredetermined location. The cylindrical member 36 is formed at itsperipheral wall with a plurality of flame-transferring holes 37. Flamegenerated by combustion of the transfer charge 8 ejects from theflame-transferring holes 37, and then ignites and burns the first gasgenerating agent provided outside the cylindrical member. It ispreferable that the cylindrical member is made of the same material asthat of the housing 3.

Especially in the gas generator shown in this embodiment, the firstcombustion chamber 50 is formed, as shown in FIG. 2, into annular shapesimilar to falcate shape whose circular inner side thereof is punchedout circularly, and the first gas generating agent 52 is disposed inthis. Therefore, unlike the second combustion chamber 60, in the firstcombustion chamber 50, a distance between the gas generating agent 52and the ignition 51 is varied depending upon a location where the gasgenerating agent 52 is accommodated. Accordingly, when the igniter 51 isignited, the first gas generating agents 52 is ignited and burntunevenly. For this reason, the directions of the flame-transferringholes 37 formed in the peripheral wall of the inner cylindrical member36 are restricted such that the flame of the transfer charge 8 isejected in the direction along an inner wall surface 50 a of the firstcombustion chamber 50 (the direction shown with the arrows in FIG. 2).With this arrangement, the gas generating agent 52 located behind thesecond combustion chamber 60 (i.e., the inner shell 4) can also be burntuniformly. In this embodiment, the inner wall surface 50 a coincideswith a surface of the coolant/filter 25.

As another example of the injecting-direction restricting means, insteadof the inner cylindrical member 36, it is possible to use a cup-likecontainer having a nozzle on the peripheral wall thereof for ejectingflame of the first ignition means (the igniter 51 and the transfercharge 8 in FIG. 1) in a direction along an inner wall surface 50 a ofthe first combustion chamber 50 (direction shown with the arrows in FIG.2). Therefore, the cup-like container as the injecting-directionrestricting means can envelop at least the ignition 51 and the transfercharge 8 to restrict the injecting direction of the flame, and is usedbeing mounted (put on) around the first ignition means. Even when suchan injecting-direction restricting means is used, it is preferable thatthe first ignition means disposed inside thereof includes a transfercharge which is to be ignited and burnt by the igniter and actuation ofthe igniter.

Another example of the injecting-direction restricting means is adeflector plate 99 shown in FIG. 34 which reflect the flame in directionshown with arrows to restrict the direction. For example, a concaveplate is placed between the combustion chamber and the housing. Thedeflector plate may be inside the filter or outside the filter. Thedeflector plate functions to control the direction of flame from thefirst igniter and also functions to control a flow of gas generated bycombustion of the gas generating agent.

The inner shell 4 defining the first combustion chamber 50 and thesecond combustion chamber 60 is of capsule-like shape as describedabove, and a plurality of opening portion 5 are formed on the peripheralwall thereof. The opening portion 5 formed such that they are openedonly by combustion of the second gas generating agent 62 disposed in thesecond combustion chamber 60, and such that they are not opened bycombustion of the first gas generating agent 52 disposed in the firstcombustion chamber 50. In the present embodiment, the opening portions 5comprise a plurality of holes 6 formed in the peripheral wall of theinner shell 4 and a breaking member 7 for closing these holes. As forthe breaking member 7, a stainless seal tape is used. The breakingmember 7 is formed such that it opens the holes 6 by being broken,peeled, burnt or detached exclusively due to the combustion of thesecond gas generating agent 62, and such that the breaking member 7 isnot broken by combustion of the first gas generating agent 52.Alternatively, as another way to prevent the opening portions of theinner shell 4 from opening by the first gas generating agent 52, it isalso possible to cover the opening portions 5 of the inner shell 4 witha shielding plate or the like which is obtained by forming a shieldingplate having appropriate shape, for example, by forming a band-likemember into annular shape, so that the flame caused by combustion of thefirst gas generating agent 52 does not come into direct contact with theopening portion 5.

Alternatively, the opening portions 5 can also be realized by forming anotch 12 in the peripheral wall of the inner shell 4 as shown in FIG.3a, or by partially reducing the thickness of the peripheral wall of theinner shell as shown in FIG. 3b. When the opening portions are opened,the first combustion chamber 50 and the second combustion chamber 60communicate with each other, and the combustion gas generated in thesecond combustion chamber 60 passes through the first combustion chamber50 and then, is discharged outside the housing 1.

The inner shell 4 is fixed by connecting an opened lower portion 13thereof to the closure shell 2. When the closure shell 2 includes acollar portion 2 a for fixing the igniter, the inner shell 4 can bemounted to the collar portion 2 a. In the gas generator shown in FIG. 1,the closure shell 2 is formed such that a circular collar portion havinga size capable of fixing two igniters is integrally connected to abottom surface of the cylindrical shell portion 2 b which is connectedto the diffuser shell 1. The inner shell 4 is connected the collarportion 2 a. The collar portion 2 a can be formed integrally on thebottom surface of the circular cylindrical shell portion 2 b as a circlehaving a size capable of fixing for each igniter. Further, the collarportion 2 a can be formed integrally on the bottom surface of thecylindrical shell portion 2 b. In such a case, the inner shell 4 candirectly be mounted to the bottom surface of the cylindrical shellportion 2 b other than the collar portion 2 a of the closure shell.

The joint of the inner shell 4 and the closure shell 2 can be performedby friction welding, crimping, resistance welding, or convex-concavejoint. When both members are joined by the friction welding, it ispreferable to join the members while fixing the closure shell 2. Withthis arrangement, even if axes of the inner shell 4 and the closureshell 2 are not aligned with each other, the friction welding can becarried out stably. If the friction welding is carried out while theinner shell 4 is fixed and the closure shell 2 is rotated, since thecenter of gravity of the closure shell 2 is deviated from the rotationcenter, the friction welding can not be carried out stably. Thereupon,in the present invention, the friction welding is carried out while theclosure shell 2 is fixed, the inner shell 4 is rotated. At the time ofthe friction welding, in order to dispose the inner shell 4 into thepredetermined position constantly, it is desirable that the closureshell 2 is positioned and fixed. Therefore, it is desirable that theclosure shell 2 is appropriately provided with a positioning means.

A gas generating agent fixing member 14 is disposed in the inner shell 4for safely and smoothly connect the closure shell 2. When the innershell 4 is friction-welded to the closure shell 2, the gas generatingagent fixing member 14 is used for preventing the gas generating agent62 from coming into direct contact with the closure shell 2 and forsecuring the installation space of the igniter 61 in a space formed bythe inner shell 4. When the inner shell 4 is mounted to the closureshell 2, it can be mounted not only by the above-described frictionwelding, but also by resistance welding, crimping, convex-concave jointor the like. In that case also, by using the gas generating agent fixingmember 14, the assembling operation is facilitated. As the gasgenerating agent fixing member 14, a canister made of aluminum havingsuch a thickness that it is easily broken by combustion of the gasgenerating agent 62. Rather than this, it is possible to use appropriatemembers to achieve the above object such as porous member using wiremesh (a material, a shape and the like are not limited). When the gasgenerating agent fixing member 14 is not used, a single-hole cylindricalgas generating agent 62 is formed into a gas generating agent solidhaving the same shape as that of the inner space of the inner shell 4,and this solid can be disposed in the inner shell 4. In this case, thegas generating agent fixing member 14 may be omitted.

In the present embodiment, the collar portion 2 a of the closure shell 2is formed into a size capable fixing the two igniters 51 and 61 side byside. With this arrangement, if the two igniters 51 and 61 arepreviously fixed to the collar portion 2 a by crimping or the like, andthe collar portion 2 a is integrally formed with the cylindrical shellportion 2 b to form the closure shell 2, the two igniters 51 and 61 canbe fixed to the closure shell 2. Although the first igniter 51 and thesecond igniter 61 are shown with the same size in the drawing, they canhave different outputs for the respective combustion chamber.

In this embodiment, as shown in a bottom view of FIG. 4, cables 15 whichare respectively connected to the igniters 51 and 61 for transmittingactuation signals are pulled out in the same direction. Positioningmeans are formed on locations where the igniters 51 and 61 are disposedso that the respective cables 15 can be specified to be connected to therespective igniters. As shown in the enlarged views of essential portionof FIGS. 5a to 5 d, such positioning means can be realized by usingconnectors 16 having different shapes for the respective igniters. Inthe positioning means shown in FIG. 5a, the connectors 16 are formedwith positioning grooves (or projections) 17, and projections (orgrooves) 18 corresponding to the positioning grooves (or projections) 17are different from each other for the respective igniters. That is,positions of the grooves (or projections) 17 of the respectiveconnectors are changed so that, at the time of mounting the connectors16 to the gas generator, if the connectors 16 are not mounted in a rightdirection, the connectors interfere with each other and can not bemounted correctly. In the positioning means shown in FIG. 5b, only oneof connectors 21 is provided with a positioning groove (or projection)19. That is, a connector 21A having the groove (or projection) 19 can beconnected to an igniter 22 b which does not have a projection (orgroove) 20, but a connector 21B which does not have the grove (orprojection) 19 can not be connected to an igniter 22 a having theprojection (or groove) 20. As a result, connection error of theconnectors 21 can be easily found at the time of assembling. In FIG. 5c,connecting portions 23 themselves of the connectors are different fromeach other. In FIG. 5d, two connectors are formed into one connector,and a positioning groove (or projection) 24 is formed. As thepositioning means, other means for eliminating connection error ofconnector can be appropriately employed.

A coolant/filter 25 as filter means for purifying/cooling the combustiongas generated by combustion of the gas generating agent is disposed inthe housing 3. Gases generated by combustion of the first and second gasgenerating agents commonly pass through the coolant/filter 25. In orderto prevent the short pass such that the combustion gas passes through aspace between the end surface of the coolant/filter 25 and the innersurface of the ceiling of the diffuser shell 1, the upper and lowerinner peripheral surfaces of the coolant/filter 25 and the inner surfaceof the housing can be covered with an inwardly-bending flange-like shortpass preventing member.

An outer layer 27 for preventing the coolant/filter 25 from expandingdue to passage of combustion gas. This outer layer 27 can be formedusing not only a laminated wire mesh body, but also a porous cylindricalmember provided at its peripheral wall surface with a plurality ofthrough-holes, or a belt-like suppressing layer comprising an annularband-like member having a predetermined width. The outer layer isprovided at its outer side with a gap 28 having a predetermined width sothat the combustion gas can pass through the entire surface of thefilter. The gas discharge port 10 formed in the diffuser shell 1 isclosed by a seal tape 29 for preventing outside air from entering. Thisseal tape 29 is ruptured when the gas is discharged. The purpose of theseal tape 29 is to protect the gas generating agent from outsidemoisture, and the seal tape 29 does not affect any performanceadjustment such as combustion internal pressure at all. The gas causedby combustion of the first gas generating agent 52 and the gas caused bycombustion of the second gas generating agent 62 both pass through thegas discharge port 10.

As shown in FIG. 6 or other drawing, as the filter means for purifyingand/or cooling the combustion gas, self-contracting type filter means 30whose upper and lower end surfaces are inclined in the outer peripheraldirection. When the self-contracting type filter means 30 is used, it ispreferable that the upper and inner surfaces 31 of the housing areinclined so as to be narrowed. As a result, the upper and lower endsurfaces of the filter means 30, when pushed radially outward bycombustion gas, abuts against the inner surface 31 of the housing, andit is possible to prevent the short pass of the combustion gastherebetween.

As described above, in the gas generator shown in FIG. 1, the igniters51, 61 and the inner shell 4 are disposed eccentrically with respect tothe housing 3. In such a gas generator, when the diffuser shell 1 andthe closure shell 2 are joined by the friction welding, by fixing theclosure shell 2 while the friction welding is carried out, both theshells can be joined stably. Especially when the inner shell 4 isdirectly mounted to the closure shell 2 by the friction welding, asshown in FIG. 7, it is preferable that the closure shell 2 is providedwith a flange portion 32 for mounting the gas generator to the modulecase and a positioning portion 34 which has their peripheries notched isformed on a portion constituting the flange portion 32 such as aprojection 33. If the positioning portion 34 is formed in this manner,since the closure shell 2 is fixed at any time in the constant directionaccording to the positioning portion 34, the inner shell 4 can reliablybe mounted to the predetermined position.

In the gas generator formed in the above-described manner, when thefirst igniter 51 which is disposed inside the first combustion chamber50 provided outside the inner shell 4 is actuated, the first gasgenerating agent 52 in the combustion chamber 50 is ignited and burnt togenerate the combustion gas. Since a gap through which the gas can passis secured between the inner shell 4 and the coolant/filter 25, thecombustion gas can pass through the entire coolant/filter 25. While thecombustion gas passes through the coolant/filter 25, the gas is purifiedand cooled and then, is discharged from the gas discharge port 10.

On the other hand, when the second igniter 61 disposed in the innershell 4 is actuated, the second gas generating agent 62 is ignited andburnt to generate the combustion gas. This combustion gas opens theopening portion 5 of the inner shell 4, and flows into the firstcombustion chamber 50 from the opening portion 5. Thereafter, thecombustion gas passes through the coolant/filter 25 and is dischargedfrom the gas discharge port 10 like the combustion gas of the first gasgenerating agent 52. The seal tape 29 closing the gas discharge port 10is ruptured by passage of the combustion gas generated in the housing 3.The second gas generating agent 62 is ignited and burnt by the actuationof the second igniter 61, and is not directly burnt by combustion of thefirst gas generating agent 52. This is because that the opening portion5 of the inner shell 4 is opened exclusively by combustion of the secondgas generating agent 62, and is not opened by combustion of the firstgas generating agent 52. However, as shown in FIG. 8, when the automaticignition material (AIM) 35 which is to be ignited by combustion heat ofthe first gas generating agent 52 transmitted from the housing 1 and thelike is accommodated in the second combustion chamber 60, the second gasgenerating agent 62 can be burnt indirectly through the combustion ofthe first gas generating agent 52.

That is, in the above-described multistage gas generator for an air bag,the first and second gas generating agents 52 and 62 are respectivelyignited and burnt by the first and second igniters independently,However, there is a case that electric current is allowed to flow onlyto the first. igniter 51 to ignite and burn exclusively the gasgenerating agent 52 in the first combustion chamber 50 intentionally.That is, the second gas generating agent 62 and the second igniter 61are left unburnt intentionally. In such a case, inconvenience is causedat the time of later disposal or damping. Therefore, it is preferablethat, after the actuation of the gas generator (only the first igniter),the gas generating agent 62 of the second combustion chamber 60 is burntat further delayed timing (e.g., 100 milliseconds or more) than thenormal delay ignition timing (e.g., 10 to 40 milliseconds) for actuatingthe second igniter 61. Thereupon, the automatic ignition material 35which is to be ignited and burnt by transmission of the combustion heatof the first gas generating agent 52 is provided in the gas generatorshown in FIG. 8. The second gas generating agent 62 is ignited by theautomatic ignition material 35 when a sufficient period of time longerthan the delayed timing (i.e., actuation interval between the igniters)when the second igniter 61 is actuated after a predetermined time lag iselapsed since the first igniter 51 is actuated. That is, this isdifferent from the case that combustion of the second gas generatingagent 62 is delayed (in other words, ignition of the second igniter isdelayed) in order to adjust the actuation performance of the gasgenerator. Further, the gas generating agent 62 is never be ignited andburnt by the automatic ignition material 35 during the period when theactuation current to the second igniter 61 is delayed arbitrarily inorder to adjust actuation performance of the gas generator. Theautomatic ignition material 35 can be combined with the second igniter61.

According to the gas generator formed in the above-described manner, theoutput mode (actuation performance) of the gas generator can be adjustedarbitrarily by adjusting the igniting timing of the two igniters 51 and61, e.g., by actuating either of the first and second igniters 51 and 61at first or by actuating both the igniters simultaneously. Therefore, invarious conditions such as speed of the vehicle and environmenttemperature at the time of collision, development of the air bag in theair bag apparatus described later can be made most suitably. Especiallyin the gas generator shown in FIG. 1, since the two combustion chambersare arranged in the radial direction, the height of the gas generatorcan be suppressed to the minimum.

Also, shapes, composition, composition ratio and amount and the like ofthe gas generating agent can be appropriately changed for obtainingdesired output mode.

Embodiment of an Air Bag Apparatus

FIG. 9 shows an embodiment of an air bag apparatus according to thepresent invention in the case of constructing the air bag apparatus insuch a manner as to include a gas generator using the electric ignitiontype ignition means.

The air bag apparatus comprises a gas generator 200, an impact sensor201, a control unit 202, a module case 203 and an air bag 204. In thegas generator 200, the gas generator described with reference to FIG. 1is used and the actuation performance thereof is adjusted so as to applyas a small impact as possible to the occupant at the initial stage ofthe actuation of the gas generator.

The impact sensor 201 can comprises, for example, a semiconductor typeacceleration sensor. This semiconductor type acceleration sensor isstructured such that four semiconductor strain gauges are formed on asilicone base plate to be bent when the acceleration is applied, andthese semiconductor strain gauges are bridge-connected. When theacceleration is applied, the beam defects and a strain is produced onthe surface. Due to the strain, a resistance of the semiconductor straingauge is changed, and the structure is made such that the resistancechange can be detected as a voltage signal in proportion to theacceleration.

The control unit 202 is provided with an ignition decision circuit, andthe structure is made such that the signals from the semiconductor typeacceleration sensor is inputted to the ignition decision circuit. Thecontrol unit 202 starts calculation at a time when the impact signalfrom the sensor 201 exceeds a certain value, and when the calculatedresult exceeds a certain value, it outputs an activating signal to theigniter 51, 61 of the gas generator 200.

The module case 203 is formed, for example, by a polyurethane, andincludes a module cover 205. The air bag 204 and the gas generator 200are stored in the module case 203 so as to be constituted as a padmodule. This pad module is generally mounted to a steering wheel 207when being mounted to a driver side of an automobile.

The air bag 204 is formed by a nylon (for example, a nylon 66), apolyester or the like, is structured such that a bag port 206 thereofsurrounds the gas discharge port of the gas generator and is fixed to aflange portion of the gas generator in a folded state.

When the semiconductor type acceleration sensor 201 detects the impactat a time of collision of the automobile, the signal is transmitted tothe control unit 202, and the control unit 202 starts calculation at atime when the impact signal from the sensor exceeds a certain value.When the calculated result exceeds a certain value, it outputs theactivating signal to the igniter 51, 61 of the gas generator 200.Accordingly, the igniter 51, 61 is activated so as to ignite the gasgenerating agent, and the gas generating agent burns and generates thegas. The gas is discharged into the air bag 204, by whereby the air bagbreaks the module cover 205 so as to inflate, thereby forming a cushionabsorbing an impact between the steering wheel 207 and the occupant.

The gas generator of eccentric structure can be realized by the AIM, thecommunication hole, the connector, the self-contracting type filter or acombination thereof. The gas generator can also be realized by combiningother parts described in the present specification.

The present invention includes a gas generator or an air bag apparatusincluding AIM, the communication hole, the connector, theself-contracting type filter. The AIM, the communication hole, theconnector, the self-contracting type filter disclosed here are suitablefor the eccentric structure and can be used in combination.

(AIM)

Namely, a gas generator for an air bag of the present inventioncomprises a housing including a gas discharge port, igniting means whichis accommodated in the housing and to be actuated on an impact, and gasgenerating means which is accommodated in the housing and to be ignitedand burnt by the ignition means and generate combustion gas forexpanding the air bag, wherein two or more combustion chambers foraccommodating gas generating means are provided being partitioned in thehousing, and the automatic ignition material (AIM) to be ignited andburnt by transmitted heat is disposed in either of the combustionchambers.

A communication hole which allows mutual communication between thecombustion chambers can also be provided.

For example, if the gas generating means accommodated in the pluralityof combustion chambers are burnt at different timing in the respectivecombustion chambers, it is preferable that the automatic ignitionmaterial (AIM) is disposed in the combustion chamber in which the gasgenerating means to be burnt at delayed timing is accommodated. In thiscase, the automatic ignition material (AIM) can be ignited and burnt bytransmitted heat generated by combustion of gas generating agent whichhas been burnt first. It is preferable that the automatic ignitionmaterial burns the gas generating agent to burn at delayed timing after100 milliseconds or longer from the point when the ignition means forigniting the gas generating means which is burnt first is actuated.Further, the automatic ignition material can be disposed in combinationwith the igniter included in the ignition means which ignites and burnsthe gas generating means which is burnt at a delayed timing (or whichmay still remain after the actuation of the gas generator).

The gas generator which burns the gas generating means in the respectivecombustion chambers at different timing can be realized by a gasgenerator in which an ignition means includes a transfer charge to beignited and burnt by the actuation of a igniter, and the transfer chargeis divided for each igniter and to be independently ignited and burnt ateach igniter, and gas generating means accommodated in the plurality ofcombustion chambers are to be ignited and burnt by flame caused bycombustion of the transfer charges in different sections.

For example, in the gas generator in which two combustion chamber foraccommodating the gas generating means are provided in the housing, thefirst gas generating means which burns first and the second gasgenerating means which burns at delayed timing are respectively disposedin the combustion chambers, and the first ignition means for ignitingthe first gas generating means and the second ignition means forigniting the second gas generating means are provided, the automaticignition material (AIM) is provided in the igniter included in thesecond combustion chamber or the second ignition means. As the automaticignition material (AIM), the material, which is ignited and burnt by theheat transmitted through the housing which is generated by combustion ofthe first gas generating means, is used.

Two combustion chambers for accommodating the gas generating means canbe provided in the housing concentrically adjacent to one another in theradial direction of the housing, and a communication hole which allowscommunication between the combustion chambers can be provided.

As the automatic ignition material (AIM) which can be used in thepresent invention, the material which can be ignited and burnt at leastby combustion heat (i.e. transmitted heat) of the gas generating means(which has been burnt first) transmitted from the housing and the like.An example of such material is nitrocellulose.

However, since these may be changed, naturally, by kinds of gasgenerating means to be used, a heat transfer member (e.g., housing) fortransmitting the combustion heat, a distance from a position where thegas generating means to be burnt first is accommodated, it is necessaryto appropriately employ these at the stage of design.

The above-described gas generator for the air bag is accommodated in amodule case together with an air bag (bag) which introduces a gasgenerated by the gas generator to expand, thereby constituting the airbag apparatus. In this air bag apparatus, the gas generator is actuatedin reaction that an impact sensor senses an impact, thereby dischargingthe combustion gas from the gas discharge port of the housing. Thecombustion gas flows into the air bag so that the air bag breaks amodule cover and expands, thereby forming a cushion between a passengerand a hard structural member of the vehicle for absorbing the impact.

Embodiment of AIM 1

FIG. 28 is a vertical cross sectional view showing another embodiment ofthe gas generator for an air bag of the present invention. The gasgenerator shown in this figure has a structure suitable to be disposedon a driver side.

In the gas generator shown in this figure, a first combustion chamber1105 a and a second combustion chamber 1105 b are defined by an innercylindrical member 1104, and are disposed adjacent to each otherconcentrically in a housing 803. The inner cylindrical member 1104 isprovided at its inner peripheral surface with a step notch 1106 at apredetermined height. A partition wall 1107 for defining the secondcombustion chamber 1105 b and an ignition means accommodating chamber1108 is disposed in the step notch 1106. In the present embodiment, asshown in an exploded perspective view in FIG. 29, the partition wall1107 comprises a sectioning circular member 1150 which engages the stepnotch 1106 of the inner cylindrical member 1104 and a seal cup member1160 which engages the sectioning circular member 1150. The sectioningcircular member 1150 is of substantially flat circular shape, andincludes an opening portion 1151 into which a transfer chargeaccommodating portion 1161 of the seal cup member 1160 is fittedinwardly, a circular hole 1152 having a bottom surface with a circularhollow for accommodating an upper portion of an igniter 1112 b, and asecond flame-transferring hole 1119 which pierces through thesubstantial center of the circular hole 1152. The seal cup member 1160includes the cylindrical transfer charge accommodating portion 1161fitting into the opening portion 1151 of the sectioning circular member1150 and projecting into the second combustion chamber 1105 b, and acylindrical igniter receiving port 1162 formed at a location opposed tothe circular hole 1152 of the sectioning circular member 1150 andextending to the opposite side from the transfer charge accommodatingportion 1161. A first transfer charge 1116 a is accommodated in thetransfer charge accommodating portion 1161, and a second igniter 1112 bis fitted into the igniter receiving portion 1162. The sectioningcircular member 1150 and the seal cup member 1160 are engaged with eachother such that the transfer charge accommodating portion 1161 of theseal cup member 1160 is fitted into the opening portion 1151 of thesectioning circular member 1150. An upper portion of the second igniter1112 b fitted through the igniter receiving port 1162 projects into thecircular hole 1152 of the sectioning circular member 1150.

The partition wall 1107 comprising the sectioning circular member 1150and the seal cup member 1160 are engaged with the step notch 1106 formedin the inner peripheral surface of the inner cylindrical member 1104 asshown in FIG. 28. That is, a peripheral edge of the sectioning circularmember 1150 is supported by the step notch 1106, and the seal cup member1160 is abutted against and supported by the sectioning circular member1150. A peripheral edge of the seal cup member 1160 is formed such as tobend in the same direction as that of the igniter receiving port 1162,and a bent portion 1163 is fitted to the groove 1164 formed in the innerperipheral surface of the inner cylindrical member 1104. With thisarrangement, the sectioning circular member 1150 is supported by theseal cup member 1160 so that movement thereof in the axial direction ofthe housing 803 is inhibited. Further, by fitting the bent portion 1163of the peripheral edge of the seal cup member 1160 into the groove 1164of the inner peripheral surface of the inner cylindrical member 1104,the partition wall 1107 (i.e., seal cup member 1160) and the innercylindrical member 1104 are engaged with each other without a gap.Therefore, in the inner cylindrical member 1104, the ignition meansaccommodating chamber 1108 provided on the side of the closure shell 802and the second combustion chamber 1105 b provided on the side of thediffuser shell 802 are reliably sectioned by the ignition means sealstructure comprising the seal cup member 1160 and the groove 1164.

The igniter receiving port 1162 formed in the seal cup member 1160 has askirt portion which spreads like a fan, and its inner side, i.e.,between the igniter receiving port 1162 and the-second igniter 1112 baccommodated in the igniter receiving port 1162, an O-ring 1181 isdisposed for sealing a space between the igniter receiving port 1162 andthe second igniter 1112 b. Further, since the O-ring 1181 is alsopressed on an under-mentioned igniter fixing member 1182, the secondigniter 1112 b is disposed in a space defined by the circular hole 1152of the sectioning circular member, the igniter receiving port 1162 ofthe seal cup member, the O-ring 1181 and the igniter fixing member 1182.When, on the actuation of the second igniter 1112 b, the seal tape 1120closing the second flame-transferring hole 1119 formed in the circularhole 1152 of the sectioning circular member 1150 is ruptured, and thedefined space communicates with the second combustion chamber 1105 b.The first igniter 1112 a and the second igniter 1112 b are reliablyseparated from each other by the seal structure (hereinafter referred as“the igniter seal structure”) comprising the skirt of the igniterreceiving port 1162, the O-ring 1181 and the igniter fixing member 1182.With this arrangement, flame generated by actuation of any of theigniters will not directly flow into the space where another igniter isaccommodated.

In the present embodiment also, the two igniters 1112 a and 1112 b arefixed to a single initiator collar 1113 such that the igniters caneasily be disposed into the housing. Especially in the presentembodiment, the two igniters 1112 a and 1112 b are supported by theigniter fixing member 1182 which engages the initiator collar 1113 andare fixed to the initiator collar 1113. The igniter fixing member 1182is formed into a shape which covers the upper surface of the initiatorcollar 1113, and has holes 1184 into which into the upper portions ofthe igniters are inserted, that support the shoulders 1183. The twoigniters 1112 a and 1112 b disposed in the initiator collar 1113 arefixed to the igniter fixing member 1182 which fits over the initiatorcollar 1113. By using such an igniter fixing member 1182, the twoigniters 1112 a and 1112 b can easily assembled into the initiatorcollar 1113. In the gas generator shown in this embodiment, the firstigniter 1112 a and the second igniter 1112 b are different from eachother in the shapes and the actuation output, but igniters having thesame actuation output can also be used.

When the gas generator shown in the present embodiment is actuated,flame generated by the actuation of the first igniter 1112 a ignites andburns the first transfer charge 1116 a disposed above the igniter. Flamegenerated by combustion of the first transfer charge 1116 a never flowsinto a space where the second igniter 1112 b is accommodated because ofthe igniter sealing structure, nor flows into the second combustionchamber 1105 b because of the ignition means sealing structurecomprising the bent portion 1163 of the seal cup member 1160 and thegroove 1164 of the inner cylindrical member 1104. Therefore, the flamegenerated by combustion of the first transfer charge 1116 a passesthrough a first flame-transferring hole 1117 formed in the peripheralwall of the inner cylindrical member 1104 and flows exclusively into thefirst combustion chamber 1105 a, and ignites and burns the first gasgenerating agent 1109 a to generate a combustion gas. Flame generated onactuation of the second igniter 1112 b passes through the secondflame-transferring hole 1119 formed in the circular hole of the dividingcircular member 1150 and flows exclusively into the second combustionchamber 1105 b, and ignites and burns the second gas generating agent1109 b to generate a combustion gas. Especially in the gas generator ofthis embodiment, the second transfer charge is not provided, and thesecond gas generating agent 1109 a directly ignited and burnt by theflame generated on actuation of the second igniter 1112 b.

Combustion gases generated by combustion of the first gas generatingagent 1109 a and the second gas generating agent 1109 b then passthrough a common coolant/filter 822 and during which, the combustion gasis purified and cooled, and is discharged from the gas discharge port826 after passing through a gap 825. Seal tapes 1118 and 1120 closingthe first and second flame-transferring holes are ruptured when theflame of the igniter and the combustion gas of the transfer charge passthrough, and the seal tape 827 closing the gas discharge port 826 isruptured when the combustion gas passes through.

In this manner, when the actuation timing of the igniters 1112 a and1112 b are staggered, and igniting timing of the gas generating agents1109 a and 1109 b, i.e., actuation performance of the gas generator isadjusted, positioning means is formed to decide the specified lead wires815′ for the respective igniters 1112 a and 1112 b. As shown in explodedperspective views of essential portions in FIGS. 30a to 30 d forexample, the positioning means can be realized by using connector 816′having different shape for each igniter. In the case of the positioningmeans shown in FIG. 30a, connectors are formed with positioning grooves(or projections) 817′, and position of projections (or grooves) 818′corresponding to the positioning grooves (or projections) 817′ aredifferent for each igniter. That is, positions of the grooves (orprojections) 817′ of the connectors are changed so that, if theconnectors 816′ are not mounted in a right direction at the time ofmounting the connectors 816′ to the gas generator, the connectorsinterfere with each other and can not be mounted correctly. In thepositioning means shown in FIG. 30b, only one of connectors 821′ isprovided with a positioning groove (or projection) 819′. That is, aconnector 821A′ having the groove (or projection) 819′ can be connectedto an igniter 822 b′ which does not have a projection (or groove) 820′,but a connector 821B′ not having the grove (or projection) 819′ can notbe connected to an igniter 822 a ′ which has the projection (or groove)820′. As a result, connection error of the connectors 821′ can easily befound at the time of assembling. In FIG. 30c, connecting portions 823′themselves of the connectors are different from each other. In FIG. 30d,two connectors are formed into one connector, and a positioning groove(or projection) 824′ is formed. As the positioning means, other meansfor eliminating connection error of connector can be appropriatelyemployed.

That is, in the gas generator of the present embodiment also, the firstand second gas generating agents 1109 a and 1109 b are respectivelyignited and burnt by the first and second igniters 1112 a and 1112 bindependently. In some cases, an electric current is applied only to thefirst igniter 1112 a to ignite and burn only the gas generating agent1109 a in the first combustion chamber 1105 a. In other words, thesecond gas generating agent 1109 b and the second igniter 1112 b areleft unburnt . This case causes inconvenience at the time of laterdisposal or damping. Therefore, it is preferable that the gas generatingagent 1109 b in the second combustion chamber 1105 b is burnt after atfurther delayed timing (e.g., 100 milliseconds or more) than the normaldelay ignition timing (e.g., 10 to 40 milliseconds) of actuating thesecond igniter 1112 b after actuation of the gas generator (the firstigniter 1112 a only). Thereupon, the automatic ignition material 1185which is ignited and burnt by transmission of combustion heat of thefirst gas generating agent 1109 a is disposed in the present invention.In such case, the second gas generating agent 1109 b is ignited by theautomatic ignition material 1185 after further sufficient time passes,which is longer than the normal predetermined delayed timing (i.e., theactuation interval between the igniters) for actuating the secondigniter 1112 b following actuation of the first igniter 1112 a. That is,it is different from the case that the second gas generating agent 1109b is burnt at the delayed timing (i.e., the second igniter is ignited atdelayed timing) in order to adjust the actuation performance of the gasgenerator. While the actuation current to the second igniter 1112 b isdelayed arbitrarily to adjust the actuation performance of the gasgenerator, the second gas generating agent 1109 b is never ignited andburnt by the automatic ignition material 1185. Besides, the automaticignition material 1185 can be provided, being combined with the secondigniter 1112 b.

The ignition timing of the automatic ignition material is determined bythermal conductivity of heat transmitting material (e.g., housing) whichtransmits the combustion heat of the first gas generating agent, adistance and the like. In this embodiment, non-azide based gasgenerating agent is used as the gas generating agent. The heattransmitting material for transmitting the combustion heat of the gasgenerating agent which burns first is the housing and/or the innercylindrical member. It is preferable that the automatic ignitionmaterial is disposed in a position near each shell in the secondcombustion chamber and more preferably, the automatic ignition materialis in contact with the shell.

The automatic ignition material may be disposed in the second combustionchamber by adhesion, or only the automatic ignition material may be putinto another container and the container may be placed in the secondcombustion chamber. It is preferable that the automatic ignitionmaterial is in contact with the heat transmitting material.

In the gas generator in which the automatic ignition material isdisposed as described above, even when only the first gas generatingagent 1109 a is burnt and the second gas generating agent 1109 bdisposed in the second combustion chamber 1105 b left unburnt after theactivation of the gas generator, it is possible to burn the second gasgenerating agent indirectly resulting from the combustion of the firstgas generating agent 1109 a, and after the actuation of the gasgenerator, disposal or damping can be carried out without any problem.

The first combustion chamber 1105 a and the second combustion chamber1105 b are defined by the inner cylindrical member 1104. The innercylindrical member 1104 is provided with a through-hole 1110 which isclosed by a stainless plate 1111. The stainless plate 1111 is adhered tothe inner cylindrical member 1104 by adhesion member such as adhesion,and the through-hole 1110 is opened only by combustion of the second gasgenerating agent 1109 b, and is never opened by combustion of the firstgas generating agent 1109 a. The reason why the through-hole 1110 isclosed by the stainless plate 1111 is to prevent a flame caused bycombustion of the first gas generating agent 1109 a from flowing intothe second combustion chamber 1105 b through the through-hole 1110 toburn the second gas generating agent 1109 b. Therefore, if such afunction can be ensured, instead of closing the through-hole 1110 by thestainless plate 1111, a breaking plate which is broken, peeled, burnt ordetached by pressure or the like due to the combustion of the second gasgenerating agent may be welded, adhered or heat-sealed to close thethrough-hole 1110, or the peripheral wall of the inner cylindricalmember 1104 may be provided with a notch, or the thickness of theperipheral wall of the inner cylindrical member 1104 maybe formedpartially thin. Further, as shown in FIG. 31, a substantially ring-likeshielding plate 1186 can be disposed such as to cover the through-hole1110 formed in the inner cylindrical member 1104. Especially in the gasgenerator shown in FIG. 31, even if the combustion gas is generated bycombustion of the first gas generating agent 1109 a, since the seal tapewhich closes the through-hole 1110 is protected by the shielding plate1186, it is not broken by combustion of the first gas generating agent1109 a. As described above, in the present embodiment, the through-hole1110 of the inner cylindrical member 1104 is opened exclusively bycombustion of the second gas generating agent 1109 b, and is neveropened by combustion of the first gas generating agent 1109 a.Therefore, even if the combustion gas is generated in the firstcombustion chamber 1105 a first, this never flows into the secondcombustion chamber 1105 b, and the gas generating agent 1109 b in thesecond combustion chamber 1105 b is ignited and burnt by the actuationof the second igniter 1112 b (combustion of the automatic ignitionmaterial 1185 in some cases) The combustion gas generated by the secondgas generating agent 1112 b passes through the through-hole 1110 whichis opened by combustion of the second gas generating agent 1112 b andpasses through the first combustion chamber 1105 a and then, purifiedand cooled by the coolant/filter 822 and discharged from the gasdischarge port 826.

In FIG. 28, the numeral 823 represents a short-pass preventing memberfor preventing the combustion gas from passing between the end surfaceof the coolant/filter and the ceiling inner surface of the diffusershell.

Connector

The present invention provides a multistage type gas generating device,wherein, in an air bag apparatus which includes a gas generator for anair bag comprising a plurality of igniters, and in which actuationsignals are outputted from a ignition signal-outputting means to each ofthe igniters, connection error between the igniters and the ignitionsignal outputting apparatus is eliminated, and the air bag apparatus canalways actuate with a desired output.

The present invention provides a multistage type air bag apparatuswherein, in a gas generating device which comprises a multistage typegas generator for an air bag including a plurality of igniters and inwhich actuation signals are outputted from ignition signal-outputtingmeans to each of the igniters by a lead wire having the connector, theconnector is provided with defining means, and, when the ignitionsignal-outputting means and the igniters are connected through the leadwires, the respective connections are specified as a unique combination.

In other words, the air bag apparatus of the present invention is amultistage type air bag apparatus comprising a multistage gas generatorstoring a plurality of electrical ignition type igniters in a housingthereof, an ignition outputting means provided with the equal numbers ofthe igniters and outputting portions for outputting an actuation signalto the igniters on an impact, and a plurality of lead wires havingconnectors, wherein the igniters and the outputting portions areconnected by the lead wires having the connectors, and said connectorshave a defining means which specifies a unique connection of therespective igniters and the respective outputting portions.

The defining means may be formed on the connector provided on at leastone end of the lead wire connecting the igniter and the outputtingportion, or the defining means may be formed on a way-connector providedat least one on the lead wire which connects the igniter and theoutputting portion.

The lead wire may be provided in the same numbers as the electricalignition type igniter provided n the gas generator. The ignition timingof each of a plurality of the igniters is individually adjusted inaccordance with environmental condition at the time of actuation of theair bag apparatus.

When the igniter includes a connecting portion for connecting theigniter to the connector, and the defining means may be formed on theconnecting portion of each of the igniters and the connector whichconnects the lead wire extending from the outputting portion to each ofthe igniters. When the outputting portion includes a connecting portionto be connected to the connector, the defining means may be formed onthe connecting portion of the outputting portions and the connectorwhich connects the lead wire extending from the gas generator to theoutputting portion. The way-connector may comprise a plug portion and ajack portion, these portions includes connecting portions, the definingmeans may be formed on the connecting portions of the plug portion andthe jack portion of the way-connector which connects the lead wireextending from the gas generator and the lead wire extending from theoutputting portion.

Conductive portions exist on the connector and the connecting portion,the respective conductive portions are brought into contact with eachother by connecting the connector and the connecting portion so thatignition signal outputted from the ignition signal-outputting means canbe transferred to each of the igniters. In this case, the defining meanscan be realized by changing at least one of a shape, the number and aposition of the conductive portion existing on the connector. Forexample, the conductive portion of the connector is of convex shape orconcave shape, and is connected to the conductive portion of theconnecting portion which is formed into a concave shape or convex shape.When the connector provided in each lead wire is made of plastic member,the plastic member maybe provided with a defining means, and the aplurality of connectors can be connected to one another by the definingmeans. The plurality of lead wires are converged into one connector, andthe connector can be provided with a defining means.

As described above, in the multistage air bag apparatus, if theconnector having the defining means is used for the lead wire forconnecting the ignition signal-outputting means and the igniter and fortransmitting the actuation signal, it is possible to specify a uniqueconnection of the respective igniters, the respective connectors and therespective actuation outputting means.

In this multistage type air bag apparatus, it is possible to use a gasgenerator having a cylindrical housing comprising a diffuser shellincluding a gas discharge port and a closure shell forming an internalspace in cooperation with the diffuser shell. A plurality of ignitersmay be arranged in the same direction as the axis of the housing, andprovided in the closure shell.

Further, the present invention also provides a multistage gas generatorfor an air bag, comprising a housing with a gas discharge port, aplurality of igniters which is accommodated in the housing and to beactuated by electric signals, and gas generating means which isaccommodated in the housing and to be burnt and/or expanded by actuationof the igniter for generating an activation gas, wherein each of theigniters includes a connecting portion for connecting to connectorsdisposed on tip ends of lead wires which transmit an activation signaloutputted from an outputting portion of ignition signal-outputtingmeans, and the connecting portion is provided with defining means whichallows only one connection of the respective connectors. Especially,this multistage type gas generator for an air bag can be preferably usedfor the multistage type air bag apparatus.

In other words, this gas generator has, when the gas generator isassembled into the air bag apparatus, the connecting portion forconnecting to connectors disposed on tip ends of lead wires whichtransmit an activation signal outputted from an ignitionsignal-outputting means, and the connecting portion is provided with adefining means which enables to connect only one of the connectors. Asan example of the defining means, the conductive portions in theigniters, which receives the actuation signal from the ignitionsignal-outputting means, are different from each other in a shape, thenumber and/or a position of for the respective igniters. With thisarrangement, only the corresponding specific connector can be connected.Alternatively, the shape of the connecting portion of the igniter can beformed into a shape which is complementarily fitted only to the specificconnector. In the latter case, a groove and/or a projection can beformed on the connecting portion so that positions and/or shapes thereofare different from each other at the respective igniters.

This gas generator is good enough as long as it includes two or moreigniters, and the gas generating means for generating the actuation gasfor expanding the air bag (bag) may be solid gas generating agent orpressurized gas. And the gas generator may be formed into either shapesuitable to be disposed on a driver side or suitable to be disposed on apassenger side. This gas generator preferably has a structure such thatcombustion chambers as many as igniters are provided in the housing, andgas generating means in each combustion chamber is burnt and expanded ateach igniter.

Further, the present invention provides a connecting method forconnecting the ignition signal-outputting means (outputting portion) andthe igniter preferably used in the above-described multistage type airbag apparatus.

That is, the present invention provides a connecting method ofconnecting a ignition signal-outputting means which includes a controlunit for sending an ignition signal to a plurality of igniters includedin a gas generator, and a plurality of ignition means included in thegas generator, wherein each of the igniters is connected to an ignitionmeans outputting apparatus through a lead wire having a connector, andconnections of the respective igniter and the respective output portionare specified by defining means.

As for the defining means, the conductive portions provided on therespective igniters are formed differently from each other in a shape,the number and/or a position at the respective igniters. Alternatively,the defining means can be realized by forming the connector and theconnecting portion so as to be fitted to each other complementarily, andthereby the combination thereof is unique. Especially, the latter casecan be realized by forming a groove and/or a projection on theconnecting portion which is different from each other in a positionand/or a shape thereof at each igniter.

Usually, modules comprising the gas generator and the air bag (bag) aredifferent in size and shape in accordance with a disposed position suchas a driver side or a passenger side, but the multistage type air bagapparatus of the invention can be used irrespective of the shape andsize of the module. Similarly, the gas generator for the multistage typeair bag of the invention can be employed to any apparatus such as for adrive side, a passenger side and a backseat regardless of variation ofshape and size.

In the multistage type air bag apparatus, any actuation signaloutputting apparatus can be used as long as it includes a plurality ofactuation signal outputting portions, the outputting timing of theactuation signal outputted from the outputting portions can be adjustedand it senses an impact and outputs the actuation signal. Therefore, theactuation signal outputting apparatus can be used as long as it includesa portion sensing the impact, and a portion for judging a degree of theimpact and controlling the output signal, without regard to a structurewhether the two portions are integrally formed or separately formed.

In the above-described multistage type air bag apparatus, for optimizingthe developing pattern of the air bag (bag), when the actuation signaloutputting means senses an impact, the outputting timing of theactuation signal is adjusted, and actuation timing of each igniterincluded in the gas generator is adjusted. At that time, since theconnectors of the lead wires connecting the ignition signal-outputtingmeans and the ignitions are provided with defining means respectively,the actuation signal outputted from the actuation signal outputtingmeans is reliably sent to the specific igniter, i.e., the igniter whichis initially planned to be actuated, no variation of actuationperformance of the air bag apparatus is caused due to connection errorof the ignition signal-outputting means and the igniter. Therefore, inthis multistage type air bag apparatus, it is possible to optimize thedeveloping pattern of the air bag more reliably.

Embodiment of Connector

The multistage gas generator for an air bag apparatus of the presentinvention will be explained based on the embodiment shown in the drawingbelow. FIG. 10 is a vertical cross sectional view showing one embodimentof the multistage type air bag apparatus of the invention.

The multistage type air bag apparatus shown in FIG. 10 comprises a gasgenerator 101 for a multistage type air bag including two igniters 108 aand 108 b, and an actuation signal outputting means 102 for outputtingactuation signal to each igniter in accordance with an impact. Amongthem, the gas generator 101 for the multistage type air bag isaccommodated in a module case 104 together with an air bag 103 which isto be expanded by introducing an actuation gas generated by actuation ofthe gas generator.

The actuation signal outputting means 102 comprises an impact sensor 105which senses an impact and a control unit 106 for inputting a signalfrom the impact sensor and outputting the ignition actuation signal.

The impact sensor 105 is for sensing the impact, and can be formed usinga semiconductor acceleration sensor for example. In the semiconductoracceleration sensor, four semiconductor strain gauges are formed on abeam of a silicon substrate which deflects if acceleration is applied,and the semiconductor strain gauges are bridge-connected. Whenacceleration is applied, the beam is bent, and strain is generated onthe surface. With this strain, resistance of the semiconductor straingauge is changed, and the resistance change is detected as a voltagesignal in proportion with the acceleration.

The control unit 106 includes an ignition judging circuit. A signal fromthe semiconductor strain gauges is inputted to the ignition judgingcircuit. When an impact signal from the sensor 105 exceeds a certainvalue, the control unit 106 starts calculation, and when the calculatedresult exceeds a certain value, an actuation signal is outputted to theigniters 108 a and 108 b of the gas generator 101.

The module case 104 is made of polyurethane, for example, and includes amodule cover 129. The air bag 103 and the gas generator 101 areaccommodated in the module case 104 to constitute a pad module. When thepad module is mounted to the driver side of an automobile, it is usuallymounted in a steering wheel 130.

The air bag 103 is made of nylon (e.g., nylon 66) or polyester and thelike, its bag port 131 surrounds a gas discharge port of the gasgenerator, and the air bag is fixed to the flange portion of the gasgenerator in a folded state.

In the multistage type air bag apparatus having the above-describedstructure, when the semiconductor acceleration sensor 105 senses animpact at the time of collision of the automobile, its signal is sent tothe control unit 106, and when the impact signal from the sensor exceedsthe certain value, the control unit 106 starts calculation. If thecalculated result exceeds the certain value, the actuation timing isadjusted, and the actuation signal is outputted to the igniters 108 aand 108 b. With this, the igniters 108 a and 108 b are actuated toignite and burn the gas generating agents for generating a combustiongas. The gas is ejected into the air bag 103, and the air bag breaks theIn module cover 129 and expands, and then forms a cushion between thesteering wheel 130 and the passenger for absorbing the impact.

The actuation signal outputted from the control unit 106 is outputtedfrom an outputting portion 107 provided in the respective igniters 108 aand 108 b in the control unit 106. The number of the outputting portions107 should be more than the number of igniters 108 included in the gasgenerator 101, i.e., two or more in the present embodiment. Foradjusting the actuation timing of the igniters, the actuation signalsfrom the outputting portions 107 a and 107 b can be outputted atdifferent timings. The actuation signals outputted from the outputtingportions 107 a and 107 b transmitted to the igniters 108 a and 108 bincluded in the gas generator 101 by the lead wires 109 a and 109 bprovided in the same numbers as the igniters 108 a and 108 b. In thiscase, if wrong lead wire 109 is erroneously connected to any of theigniter, desired actuation output can not be obtained. Thereupon, thelead wires 109 a and 109 b for connecting the outputting portions 107 aand 107 b and the igniters 108 a and 108 b are provided with connectors110 a and 110 b, and connectors 110 a and 110 b are provided withdefining means. with this arrangement, actuation signal outputted fromthe first outputting portion 107 a is reliably sent to the first igniter108 a, and actuation signal outputted from the second outputting portion107 b is reliably sent to the second-igniter 108 b. The defining meanscan be formed differently in accordance with a structure of the igniter108 and the control unit 106 or a shape of the lead wire 109 forconnecting the igniter 108 and the outputting portion 107.

In the multistage type air bag apparatus of FIG. 10, as shown in FIG.11, when the connectors 110 a and 110 b are mounted to tip ends of thelead wires 109 a and 109 b respectively extending from the outputtingportions 107 a and 107 b, and the respective connectors 110 a and 110 bare connected to connecting portions 111 a and 111 b of the igniter 108a and 108 b, connectors 110 a and 10 b and the connecting portions 111 aand 111 b can be provided with defining means as shown in FIGS. 12 and13. When the connector 110 of the lead wire 109 is connected to theigniter in this manner, a conductive portion i.e., a conductive pin 112,which receives the actuation output from the control unit 106, is used.

In the defining means shown in FIG. 12, shapes of the connecting portionare different from each other at the respective igniters, or a grooveand/or a projection are formed so that positions and/or shapes thereofare different from each other at the respective igniters. In the case ofthe defining means shown in FIG. 12a, positioning grooves (orprojections) 117 are formed on the connectors 110 a and 110 b, andpositions where projections (or grooves) 118 corresponding to thepositioning grooves (or projections) 117 are different from each otherat each igniter. In the case of the defining means shown in thisdrawing, positions of the grooves (or projections) 117 of the connectorsare different from each other so that, at the time of mounting theconnectors 110 a and 110 b to the gas generator, if the connectors arenot mounted in the right direction, the connectors interfere with eachother and they can not be mounted right. In the defining means shown inFIG. 12b, only one connector 110 b is provided with a positioning groove(or projection) 119. That is, a connector 110 b having the groove (orprojection) 119 can be connected to an igniter 108 a which does not havea projection (or groove) 120, but a connector 110 a which does not havethe grove (or projection) 119 can not be connected to an igniter 108 bhaving the projection (or groove) 120. As a result, connection error ofthe connectors can easily be found at the time of assembling. In FIG.12c, the shapes of connecting portions 116 of the connectors 110 a and110 b are different from each other. In FIG. 12d, two connectors areformed into one connector, and a positioning groove (or projection) 124is formed.

As the gas generator shown in FIG. 11, when the conductive pin 112 isprovided as the conductive portion on the connecting portion to whichthe connector is connected and the conductive portion (the conductivepin 112) of the connecting portion 111 is connected to the conductiveportion of the connector 110 so that current can flow, the shape, thenumber or the position of the conductive pin 112 can be changed in eachigniter, and in accordance with this, the shape, the number or theposition of the conductive portion of the connector 110 can be changed.

FIG. 13 shows a mode of the conductive pins different from each other atthe respective igniters. FIG. 13a shows that the shapes of theconductive pins 112 of the igniters 108 a and 108 b are different, andFIG. 13b shows that the conductive pins 112 of the igniters 108 a and108 b are formed at the different positions. Such mode of conductivepins can be appropriately employed as long as the respective ignitershave different conductive pins form each other. In this case, the shape,the position or the number of the conductive portions of the connectors110 a and 110 b are adjusted in accordance with a mode of the conductivepins 112 of the igniters 108 a and 108 b. When the conductive pins 112of the igniters 108 a and 108 b are formed at the different positions asshown in FIG. 13b, the connectors 110 a and 110 b can also be connectedas shown in FIG. 13c.

When the defining means are provided to connect the igniters and theconnectors 110 a and 110 b as described above, the connectors 110 a and110 b are preferably designed so that the lead wires 109 a and 109 bwhich are connected to the respective connectors 110 a and 10 b arepulled out in the same direction and further, that direction isperpendicular to the center axis of the housing.

Further, in the multistage type air bag apparatus shown in FIG. 10, whenthe ends of the lead wires 109 a and 109 b are provided with connectors113 a and 113 b, and the connectors 113 a and 113 b are respectivelyconnected to connecting portions 114 a and 114 b of the outputtingportions 107 a and 107 b as shown in FIG. 14, the connectors 113 a and113 b and the connecting portions 114 a and 114 b can be respectivelyprovided with defining means similar to those of the igniters shown inFIG. 12. Namely, shapes of the connecting portions 114 a and 114 b ofthe outputting portions 107 a and 107 b are different at the respectiveconnectors 113 a and 113 b, or grooves and/or projections which aredifferent in position and/or shape are formed. In accordance with theconnecting portions 114 a and 114 b of the outputting portions 107 a and107 b, in this case, the connectors 113 a and 113 b are formed in shapeto have positions and/or into shapes of the grooves and/or theprojections respectively. Further, when the connecting portions 114 aand 114 b of the outputting portions 107 a and 107 b have conductivepins 115 a and 115 b which functions as the conductive portions, theconductive pins 115 a and 115 b can be formed into the mode shown inFIG. 13. In this manner, in the case of the multistage type air bagapparatus in which the connector 113 of the lead wire 109 is connectedto the ignition signal-outputting means (the control unit 106 in thepresent embodiment), by providing the connecting portions 114 a and 114b of the outputting portions 107 a and 107 b and the connectors 113 aand 113 b with the defining means, the lead wire 109 a is connected tothe first outputting portion 107 a through the connector 113 a, and thelead wire 109 b is connected to the second outputting portion 107 bthrough the connector 113 b. Therefore, when the igniters 108 a and 108b are connected to the lead wires 109 a and 109 b respectively, byproviding the defining means shown in FIGS. 12 and 13, the actuationsignal outputted from the first outputting portion 107 a is inputted tothe first igniter 108 a without mistake, and the actuation signaloutputted from the second outputting portion 107 b is inputted to thesecond igniter 108 b without mistake. With this arrangement, in themultistage type air bag apparatus, a desired actuation performance canbe obtained reliably.

Further, in the multistage type air bag apparatus shown in FIG. 10, asshown in FIG. 15, when way-connectors 125 a and 125 b are connected tothe intermediate portions of the lead wires which connect the outputtingportions 107 a and 107 b of the ignition signal-outputting means (thecontrol unit 106 in the present embodiment) and the gas generator forthe multistage type air bag (the igniter 108 in the present embodiment),the way-connectors 125 a and 125 b can also be provided with definingmeans. That is, the defining means as explained in FIGS. 12 and 13 areprovided in a plug 125 a 1 and a jack 125 a 2 of the way-connector 125a, and in a plug 125 b 1 and a jack 125 b 2 of the way-connector 125 b.Such defining means can be realized by adjusting the shape of theconnector itself or by providing or not providing concave and convex, oradjusting the position, shape and the like of the conductive pin so thatthe plug 125 a 1 can be connected only to the jack 125 a 2, and the plug125 b 1 can be connected only to the jack 125 b 2. More specifically, asshown in FIG. 16(a), the locations where the conductive pins 121 of theplugs 125 a 1 and 125 b 1 can be set different from each other at therespective way-connectors 125 a and 125 b. Alternatively, as shown inFIG. 16(b), shapes of the conductive pins 121 of the plugs 125 a 1 and125 b 1 can be made different from each other at the respectiveway-connectors 125 a and 125 b. Or as shown in FIG. 16(c), the shapes ofthe connectors 125 a and 125 b can be made different from each other.For example, as shown in FIG. 17, the method of providing the definingmeans to such way-connectors can be employed also when the igniters 126a and 126 b provided in the gas generator do not directly connect theconnectors. In other words, when the igniters include a connectingportion for connecting the connector, the defining means can be providedby the method as shown in FIGS. 12 and 13, but when the lead wires 127 aand 127 b are connected directly to the igniters 126 a and 126 b asshown in FIG. 17, it is difficult to connect the connectors directly tothe igniters 126 a and 126 b. Thereupon, the lead wires 127 a and 127 bextending from the igniters 126 a and 126 b are provided at their tipends with the connectors 128 a and 128 b, and the way-connectors 125 aand 125 b are connected to the connectors. If the connectors arerespectively provided with the defining means and the way-connector 125a is connected to the connector 128 a and the way-connector 125 b isconnected to the connector 128 b, the actuation signal sent from thefirst lead wire 126 a is reliably transmitted to the first igniter 126a, and the actuation signal sent from the second lead wire 126 b isreliably transmitted to the second igniter 126 b.

By the above-described structure and method, in this multistage type airbag apparatus, connection error of the outputting portion and theignition is eliminated, and the actuation signals of the ignitersoutputted from the outputting portions 107 a and 107 b of the controlunit 106 in the ignition signal-outputting means can be transmitted tothe desired igniters. Therefore, according to this multistage type airbag apparatus, a desired actuation performance can reliably be obtained.

FIG. 18 is a vertical cross sectional view showing an embodiment of amultistage type air bag apparatus preferably used for theabove-described multistage type air bag apparatus. Namely in this gasgenerator, the multistage type air bag is provided with defining meanswhich can specify the connectors 110 a and 110 b mounted to tip ends ofthe lead wires connected to the ignition signal-outputting means and canconnect the connectors, as explained in the above.

In this gas generator, two combustion chambers 133 a, b foraccommodating gas generating agents are provided in a housing 132, andtwo igniters 135 a, b for burning gas generating agents 134 a, bdisposed in the respective combustion chambers are accommodated. Theigniters disposed in the housing can be actuated independently, and whenone of the igniters is actuated, the gas generating agent in one of thecombustion chambers is ignited and burnt. That is, this gas generator isadapted such that the gas generating agents 134 a, b in the combustionchambers 133 a, b are ignited and burnt only by either one of theigniters 135. Therefore, if the actuation timings of the igniters 135 a,b are adjusted, the burning timings of the gas generating agents 134 a,b in the combustion chambers can be adjusted, and with this feature, theactuation performance of the gas generator and the air bag apparatus canbe adjusted. More specifically, when the first igniter 135 a isactuated, the transfer charge 136 is burnt, the flame is ejected fromfirst flame-transferring hole 150 into the first combustion chamber 133a to ignite and burn the first gas generating agent 134 a accommodatedin the first combustion chamber. The second igniter 135 b is actuatedsimultaneously with or slightly later than the first igniter, and theflame passes through the second flame-transferring hole 150 b andejected into-the second combustion chamber. The second gas generatingagent is ignited and burnt by this flame to generate the actuation gas,and the gas passes through the through-hole 152 of the inner cylindricalmember 151 and is ejected into the first combustion chamber 133 a. Theactuation gas generated by combustion of the first gas generating agent134 a and the second gas generating agent 134 b is purified and cooledwhile the gas passes through the coolant/filter 137 and discharged fromthe gas discharge port 153.

In this gas generator, the transfer charge 136 capable of being ignitedand burnt by the actuation of the igniter 135 to efficiently burn thegas generating agent can be combined in the igniter 135. When the gasgenerating agent 134 is burnt and combustion residue is also generated,a filter for purifying the combustion residue can be disposed, and acoolant for cooling the combustion gas can be disposed. In the presentembodiment, the coolant/filter 137 for purifying and cooling thecombustion gas is used.

In this gas generator, the two igniters are respectively accommodated inigniter collars 138 and disposed in the housing 132. In the ignitercollar, the position where the igniter 135 is accommodated is providedwith a connecting portion 139. Connectors 110 of tip ends of the leadwires 109 extending from the ignition signal-outputting means arerespectively connected to the connecting portions when the air bagapparatus is formed using the gas generator.

In the gas generator of the present invention, the connecting portion139 is provided with a defining means 140 so that among the plurality ofconnectors 110 a, b for transmitting the actuation signals from theignition signal-outputting means to the igniters 135 a, b, the connector110 a capable of being connected to the connecting portion 140 can bespecified. That is, the defining means 140 of the igniter 110 a, b areformed differently at the respective igniters 110 a, b. For example, asshown in FIG. 12, the shapes of the connecting portions 139 a, b of theigniters 125 a, b can be formed differently from each other, or groovesand/or projections having different positions and/or shapes can beformed. Further, as shown in FIG. 13, shapes, positions or the like ofthe conductive pins 141 of the igniters projecting into the connections139 a, b can be set different from each other at the respective igniters135 a, b.

Although the gas generator suitable to be disposed on a driver side hasbeen described in the present embodiment, a gas generator which is longin the axial direction suitable to be disposed on a passenger side, or agas generator using pressurized gas instead of solid gas generatingagent can be used as long as the gas generator includes two or moreigniters.

The two igniters may not be always disposed on the same plane as shownin FIG. 18, and the igniters can also be disposed on different planes,e.g., on the upper surface and the lower surface of the gas generator.

Self-contracting Type Filter

Filter means of a gas generator for an air bag of the present inventionis substantially cylindrical shape as a whole, and at least any ofaxially end surface is formed such as to be inclined and narrowedoutwardly in the radial direction. This filter means expands radiallyoutward by the actuation gas generated by the actuation of the gasgenerator. By this expansion, the filter means abuts against thesupporting portion and/or supporting member in the housing, and thefilter means is contracted in the axial direction by the inclination ofthe end surface, and at the time of actuation of the gas generator, theshort pass of the actuation gas at the end surface of the filter meanscan be prevented.

That is, the filter means of the gas generator for the air bag of thepresent invention is disposed in the housing of the gas generator forthe air bag, and the cylindrical filter means is for purifying and/or acooling an activation gas, one or both of axial end surfaces of thefilter means are formed as inclining end surfaces which get narrower inan axial extending direction and the interior angle with respect to theinner peripheral surface is an acute angle. Especially, since thisfilter means expands outwardly in the radial direction by the actuationgas generated on the actuation of the gas generator, it is preferablethat the filter means is made of wore rods, and formed so as to expandand contract in the radial direction.

Such filter means includes any filter means, having a opening throughwhich the actuation gas passes, such as the filter used for cooling theactuation gas when a temperature of the gas is high and, in addition, afilter for purifying the combustion residue included in the actuationgas, and a coolant/filter having both the functions. The filter means issubstantially cylindrical shape as a whole, and one or both of axial endsurfaces of the filter means are formed as inclining end surfaces. Theinclining end surfaces are inclined so as to be narrowed in the axialextending direction of the filter means. More specifically, if the upperend surface is inclined, it is inclined so as to descend outwardly inthe radial direction, and if the lower end surface is inclined, it isinclined so as to ascent outwardly in the radial direction. That is, thefilter means comprises an inclining portion formed with an inclined endsurface, and a straight body portion axially connected to the incliningportion to form a peripheral surface. The inclining portion can beprovided on the both sides of the straight body portion in the axialdirection, or on either side of straight body portion.

This filter means can be formed by laminating cylindrically a wire meshmade of various wire rods to form a laminated wire mesh filter, and thencompress-molding the filter. An example of the wire mesh made of wirerods is preferably a stainless steel wire mesh, and as the stainlesssteel of the wire mesh material, SUS304, SUS310S, SUS316 (in theJapanese Industrial Standards codes) and the like can be used. SUS304(18Cr-8Ni-0.06C) exhibits excellent corrosion resistance as anaustenitic stainless steel. If such a filter means made of wire rods isformed to expand and contract at least in the radial direction, furtherremarkable effects can be obtained.

Further, the present invention provides, a gas generator for air bag foreffectively preventing the short pass of the actuation gas using theabove-described filter means.

That is, a gas generator for an air bag of the present inventioncomprises, in a housing with a gas discharge port, a igniting means tobe actuated on an impact, a gas generating means for generating anactivation gas to expand the air bag due to actuation of the ignitionmeans and a cylindrical filter means for purifying and/or cooling theactivation gas, wherein in said filter means, one or both of axial endsurfaces are formed as inclining end surfaces which get narrower in anaxial extending direction and the interior angle with respect to theinner peripheral surface is an acute angle, and a supporting portionwhich is opposed to the inclining end surface of the filter exists inthe housing.

As the supporting portion provided in this housing, for example, theinner surface of the housing opposed to the inclining end surface of thefilter means, i.e., the inner surface where the inclining end surface ofthe filter means are provided as well as in the axial direction of theposition where the filter means are provided, an inclining surfacehaving substantially the same inclination as the inclining end surfaceof the filter means are formed as the supporting portion of the housing.Alternatively, a filter means supporting member which has a incliningside opposed to the inclining end surface of the filter means isdisposed in the housing in the axial direction of the filter means endsurface and on the side where the inclining end surface of the filtermeans is formed, and thereby, the inclining surface of the filter meanssupporting member can be the above supporting portion.

As the filter means, the one whose end surfaces of the axially oppositesides are formed as inclining end surfaces can be used. Alternatively,the filter means whose either of end surfaces of axially opposite sidesformed into the inclining end surface. In other words, the filter meanscomprises a straight body portion forming the peripheral surface and aninclining portion formed with an inclining end surface. The incliningportion is provided on either or both sides of the straight portion inthe axial direction. When the filter means formed at its axially bothend surfaces with the inclining end surfaces (inclining portions) isused, the supporting portions provided in the housing are provided onaxially both sides where the filter means is disposed. When the filtermeans formed at its axially one end surface with the inclining surface(inclining portion), the supporting portion provided in the housing isprovided in the axial direction of the filter means as well as on theside of the inclining surface (inclining portion) of the filter means.In this case, it is preferable that a retainer having an annular portionand an outer peripheral wall is disposed in the housing on the axiallyopposite side of the supporting portion, i.e., the opposite side of theinclining end surface, with respect to the filter means end surface, andan inner surface of the outer peripheral wall of the retainer is opposedto an outer peripheral surface of the filter means end. Instead ofdisposing the retainer, the outer diameter on the end surface where theinclining end surface of the filter means is not formed can be formedlarger so that the end surface abuts against the inner surface of theperipheral wall of the housing.

When it is not desired that the straight portion of the filter means isexpanded and deformed, e.g. , when it is desired to ensure a spacebetween the inner surface of the housing and an outer surface of thefilter means, the straight portion may be provided at its outerperipheral surface with expansion-suppressing means comprising apunching metal or a winding of a porous cylindrical shape to prohibitexpansion thereof. In this case, only the inclining portion of thefilter means expands and then abuts against and is supported by thesupporting portion (material).

The gas generator of the present invention is not limited by the entireshape thereof. Therefore, for example, the gas generator having acylindrical shape which is long in the axial direction or the gasgenerator having a cylindrical shape which is wide in the radialdirection can be used. As the ignition means disposed in the housing, aslong as it is actuated on an impact, an igniter which is actuatedelectric signal output by an impact, any known igniter, which is used tomake the gas generating means generate an actuation gas, such as anigniter to be activated by an electrical signal outputted on an impact,or a combination of said igniter and a transfer charge to be ignited andburnt by actuation of the igniter, can be used.

Examples of the gas generating means which is accommodated in thehousing for generating the actuation gas to expand the air bag on theactuation of the ignition means are a solid gas generating agent whichis to be ignited and burnt by the actuated ignition means to generate anactuation gas, a pressurized gas which is heated to expand and generatean actuation gas, and a combination. As the gas generating agent, aconventionally and widely used azide-based gas generating agent based oninorganic azide such as sodium azide, or a non-azide-based gasgenerating agent not based on inorganic azide can be used. Further, asthe pressurized gas, a known gas such as a mixture of oxygen and inertgas can be used. That is, the gas generator of the present invention canbe realized by both of a pyrotechnic gas generator using a solid gasgenerating agent, and a hybrid gas generator using pressurized gas aswell as solid gas generating agent.

The gas generator of the present invention is actuated so that, afterthe ignition means is actuated, the actuation gas is generated form thegas generating means, the actuation gas is purified and cooled while itpasses through the filter means and then, the gas is discharged form thegas discharge port. When the actuation gas passes through the filtermeans, the filter means expands in the radial direction due to thepressure of the actuation gas, but in the gas generator, the axially oneor both end surfaces of the filter means is formed as the incliningsurface which is inclined so as to be narrowed outwardly in the radialdirection, and the supporting portion having the inclining surface whichis opposed to the inclining surface of the filter means is provided inthe housing. Therefore, the inclining surface of the filter means whichexpands in the radial direction abuts against the supporting portion inthe housing, and the filter means is slightly contracted in the axialdirection by this inclination. With this, the end surface of the filtermeans is strongly brought into contact with the supporting portion withpressure, and the short-pass of the actuation gas between the incliningsurface (i.e., end surface) of the filter means and the supportingportion can be prevented.

As realized also in the gas generator having the above-describedstructure, manufacturing cost can be reduced by employing the method ofa purifying and/or cooling an actuation gas wherein a supporting portionwhich is inclined so as to be narrowed in the axial extending directionof the housing is provided in the housing, the cylindrical filter meansexpanded radially by passage of the actuation gas is contracted in theaxial direction by inclination of the supporting portion and is abuttedagainst the supporting portion, and thereby preventing the activationgas from passing between the filter means and the supporting portion.

The above-described gas generator is accommodated in the module casetogether with the air bag (bag) to expand by a gas generated by the gasgenerator, and combined with the impact sensor for sensing at least animpact to actuate the gas generator, thereby constituting the air bagapparatus. In this air bag apparatus, the gas generator is actuated asan impact sensor senses an impact, thereby discharging the combustiongas from the gas discharge port of the housing. The combustion gas flowsinto the air bag so that the air bag breaks a module cover and expandsto form a cushion between a passenger and a hard structural member inthe vehicle for absorbing the impact.

Embodiment of Self-contracting Type Filter 1

FIG. 19 is a vertical cross sectional view showing one embodiment of agas generator for an air bag of the present invention. Especially, thegas generator shown in this drawing is a pyrotechnic type gas generatorfor generating the actuation gas by combustion, and has a structurewhich is longer in its diametrical direction than in the axialdirection.

In the gas generator shown in the present embodiment, a diffuser shell301 having a gas discharge port 310 and a closure shell 302 forming aninternal space in cooperation of the diffuser shell are joined to eachother to form a substantially cylindrical housing 303. An innercylindrical member provided at its peripheral wall with a plurality ofthrough-holes 320 is disposed in the housing 303 concentrically. Theoutside of the inner cylindrical member 304 is formed as a firstcombustion chamber 305 a. Inside of the inner cylindrical member isdivided into two chambers by a partition wall 321 comprising a seal cupmember 106 and a dividing circular member 307, and the two chambers areadjacent to each other in the axial direction. One of the chamberscloser to the diffuser shell 301 is a second combustion chamber 305 b,and the other chamber closer to the closure shell 302 is an ignitionmeans accommodating chamber 308. Gas generating agents 309 are disposedin the first and second combustion chambers, and the gas generatingagents disposed in the combustion chambers are independently ignited andburnt by the actuation of two igniters 311 a, b disposed in the ignitionmeans accommodating chambers.

A filter means 350 of one embodiment of the present invention is used inthe housing 303. FIG. 20 shows a partial sectional view of the filtermeans 350. In the filter means having substantially cylindrical shape asa whole, axially opposite end surfaces thereof are inclined, beingnarrowed in the axial extending direction, to form an inclining endsurface 351 whose interior angle θ with respect to the inner peripheralsurface is acute angle. More specifically, the upper end surface thereofis inclined so as to descend outwardly in the radial direction, and thelower end surface thereof is inclined so as to ascend outwardly in theradial direction. This filter means 350 can be made by laminatingcylindrically wire mesh made of various wire rods to form a laminatedwire mesh filter, and then compress-molding the filter. As shown in FIG.19, the filter means 350 is disposed in the housing so as to be opposedto an inner peripheral surface of the housing 301. A supporting member353 having an inclining surface 352 opposed to an inclining end surface351 of the filter means is disposed in the housing in the axialdirection of the end surface of the filter. The inclining surface 352 ofthe supporting member 353 functions as a supporting portion of thefilter means 350. That is, in this embodiment, the filter means 350whose both axially opposite ends are formed as the inclining endsurfaces 351 is used, and the filter means supporting members 353 areprovided on axially opposite sides of the filter means in the housing.The inclining surface 352 of the filter means supporting member 353abuts and supports the inclining end surface 351 of the filter means 350which expands in the radial direction.

A partition wall 321 defining an interior of the inner cylindricalmember into the second combustion chamber 305 b and the ignition meansaccommodating chamber 308 comprises a seal cup member 306 and asubstantially flat plate-like dividing circular member 307. A transfercharge accommodating portion 312 provided in the seal cup member 306 iscombined so as to project from an opening portion 313 of the dividingcircular. member. The partition wall 321 is engaged with and fixed to astep notch 314 of the inner cylindrical member. The seal cup member 306includes a cylindrical igniter receiving port 315 extending into theopposite side of the transfer charge accommodating portion 312, and asecond igniter 311 b is accommodated in the igniter receiving port 315.

The first igniter 311 a and the second igniter 311 b are accommodated inan initiator collar 316, and supported by and fixed to an igniter fixingmember 317 which covers the collar 316. The igniter receiving port 315of the seal cup member 306 is located in the vicinity of the igniterfixing member 317, and an O-ring 325 is disposed therebetween. With thisarrangement, sealing between the first igniter 311 a and the second ii311 b, as well as between the second combustion chamber 305 b and thehousing are realized.

This gas generator is actuated in such a manner that, on actuation ofthe first igniter 311 a, the first transfer charge 318 accommodated inthe transfer charge accommodating portion 312 of the seal cup member 306a is ignited and burnt, the flame is discharged from the firstflame-transferring hole 319 a provided in the inner cylindrical member304 into the first combustion chamber 305 a to ignite and burn the firstgas generating agent 309 a. The second igniter 311 b accommodated in theigniting means accommodating chamber 308 is actuated simultaneously withor slightly later than the first igniter 311 a, the flame is dischargedinto the second combustion chamber 305 b from the second flametransferring hole 319 b formed in the dividing circular member 307,thereby burning the second gas generating agent 309 b. The actuation gasgenerated by combustion of the second gas generating agent is dischargedinto the first combustion chamber 305 a from the through-hole 320provided in the inner cylindrical member 304.

The actuation gas generated by combustion of the first gas generatingagent 309 a and the second gas generating agent 309 b passes through thefilter means 350 disposed so as to surround radially the outer side ofthe first combustion chamber 305 a, and during that period, a combustionresidue is collected and the gas is cooled. At that time, the filtermeans 350 slightly expands outwardly in the radial direction due to thepressure and the like of the actuation gas. The expanded filter means isabutted against and supported by the filter means supporting member 353which is disposed in the axial direction of the filter, and the shortpass of the actuation gas such that the actuation gas passes through thegap between the filter means end surface and the filter means supportingmember 353 can be prevented. Namely, the filter means 350 is aself-contracting type filter which is contracted by itself due topassage of the actuation gas. The actuation gas which has passed throughthe filter means 350 breaks the seal tape 322 which closes the gasdischarge port 310, and is discharged out from the housing through thedischarge port 310.

In the gas generator of the present embodiment, known gas generatingagents 309 a, b, transfer charge 318, igniters 311 a, b and the like canbe used.

In the present embodiment, it is possible to use filter means providedat its only one side with the inclining surface as shown in FIG. 21,i.e., a filter means 355 which is substantially cylindrical shape as awhole, and axially one end surface thereof adjusted to be inclined,being narrowed in the axial extending direction, to form an incliningend surface 351 whose interior angle θ with respect to the innerperipheral surface is an acute angle. However, in this case, as shown inFIG. 22, the filter means supporting member 353 disposed in the housing303 is disposed only on the side where the inclining end surface 351 ofthe filter means is formed, and a retainer 324 comprising an annularportion 323 b and a wall surface portion 323 a having the inner andouter peripheries is disposed on the opposite side (i.e., on the closureshell 302 side). A outer peripheral skirt portion 354 of the filtermeans is abutted against and supported by an inner surface of an outerperipheral wall 323 a of the retainer.

In the gas generator shown in FIG. 22, if the actuation gas is generatedby the burning of the first and second gas generating agents, theactuation gas expands the filter means 355 outwardly in the radialdirection when the gas passes through the filter means as the gasgenerator shown in FIG. 19. The radially expanded filter means 355 isabutted at its inclining end surface 351 against the inclining surface352 of the filter means supporting member 353, the outer peripheralskirt portion 354 is abutted against the inner surface of the outerperipheral wall of the retainer 324. Therefore, this filter means 355also becomes a self-contracting type filter which is contracted byitself by passage of the actuation gas due to the inclining end surface352 formed on the upper end surface.

Embodiment of Self-contracting Type Filter 2

A gas generator shown in FIG. 23 is characterized in that an incliningsurface 452 which is inclined so as to be narrowed outwardly in theradial direction is formed on the inner surface of the housing 403. Thisinclining surface 452 is formed inside the housing axially on the sidewhere the inclining surface of the filter means is formed. In thepresent embodiment, the inclining surface functions as a supportingportion of the filter means, and this is provided by forming aninclining portion which inclines in a chamfering shape on a peripheraledge of a circular portion 461 of the housing 403.

In the gas generator shown in this embodiment, the housing 403 comprisesa diffuser shell 401 having a gas discharge port 410 and a closure shell402 forming an interior space in cooperation with the diffuser shell. Asubstantially cylindrical inner cylindrical member 404 provided at itsperipheral wall with a plurality of through-holes 420 is disposed in thehousing 403, and outside of the cylindrical member is defined as acombustion chamber 405 and inside thereof is defined as an ignitionmeans accommodating chamber 408. A gas generating agent 409 forgenerating the actuation gas by combustion is accommodated in thecombustion chamber 405. An ignition means comprises an igniter 411 and atransfer charge 418 is disposed in the ignition means accommodatingchamber 408. Disposed radially outside of the combustion chamber 405 isfilter means 355 provided at its only one side with the incliningsurface as shown in FIG. 21, i.e., filter means 355 which issubstantially cylindrical shape as a whole, and axially one end surfacethereof is inclined, being narrowed in the axial extending direction, toform an inclining end surface 351 whose interior angle θ with respect tothe inner peripheral surface is an acute angle.

Especially in this embodiment, a filter means supporting member as shownin Embodiment 1 is not disposed in the axial direction of the incliningend surface 351 of the filter means 355. This is because that theinclining surface 452 against which the inclining end surface of thefilter means abuts is formed in the housing 403 at a location where thefilter means 355 is disposed and the inclining end surface 351 isformed. Therefore, in this embodiment, the inclining surface 452functions as the supporting portion of the filter means 355.

The housing 403 having such an inclining surface can be realized bypress-molding various metal plates such as a stainless steel plate, anickel plated steel plate and an aluminum alloy plate to form thediffuser shell and the closure shell, and forming the inclining portion453 on the shell (diffuser shell 401 in the present embodiment) on theside of which the inclining surface 351 of the filter means 355 isprovided.

In the present embodiment, the diffuser shell 401 constituting thehousing comprises a circular portion 461 forming a ceiling surface, aninclining portion 453 which is inclined so as to spread like a fanoutwardly in the radial direction from the outer periphery of thecircular portion, a peripheral wall 462 bent from a tip end of theinclining portion and extended downward, and a flange portion 463bending from the lower end of the peripheral wall and spreading radiallyoutward of the housing. The closure shell 402 comprises an annularportion 465 provided at its central portion with a hole 464 in which theinner cylindrical member 404 is included, a peripheral wall 466 risingfrom the outer peripheral edge of the annular portion in the axialdirection of the housing, and a flange portion 467 bending from theupper end of the outer peripheral wall and spreading radially outward ofthe housing. The flange portions of both the shells are joined to eachother by various welding methods to form the housing. The diffuser shell401 is formed at its peripheral wall surface with a plurality of gasdischarge ports 410 for discharging the actuation gas, and the gasdischarge ports are closed by moisture-proof seal tape 422. A tape whichis ruptured by the actuation gas is used as the seal tape 422.

In the housing formed in this manner, an inner surface of the incliningportion 453 of the diffuser shell 401 is also formed as an incliningsurface spreading downward like a fan, and more specifically, as theinclining surface 452 inclining downward radially outward. The filtermeans 355 is disposed in the housing 403 so that its inclining endsurface 351 is opposed to the inclining surface 452. The incliningsurface 452 formed on the inner surface of the housing functions as asupporting member of the filter means like the inclining surface of thefilter means supporting member of Embodiment 1, and abuts and supportsthe inclining end surface 351 of the filter means which expandsoutwardly in the radial direction due to passage of the actuation gas.

In the present embodiment also, like the gas generator shown in FIG. 22,a retainer 424 comprising a flat plate annular portion 422 and a wallsurface 423 provided at its inner periphery and outer periphery isdisposed on an end surface of the filter means 355 on the side where theinclining end surface is not formed. The outer peripheral skirt portionof the filter means is abutted against and supported by an inner surfaceof the outer peripheral wall 423 of the retainer 424.

According to the gas generator shown in this drawing, when the igniter411 is actuated, the transfer charge 418 disposed above the igniter 411is ignited and burnt, and the flame is ejected from the through-hole 420of the inner cylindrical member 404 into the combustion chamber 405 inwhich the gas generating agent 409 is accommodated. The flame of thetransfer charge 418 ejected into the combustion chamber ignites andburns the gas generating agent 409, thereby generating the actuation gasfor expanding the air bag. This actuation gas is purified and cooledwhile it passes through the filter means 355, and breaks the seal tape422 and is discharged from the gas discharge port 410.

While the actuation gas passes through the filter means 355, the filtermeans is expanded radially outward due to the pressure. If the filtermeans 355 is expanded radially outward, its inclining end surface 351abuts against the inclining surface 452 of the housing inner surface,and it is possible to prevent the short pass of the actuation gasbetween the filter means end surface (the inclining end surface 351) andthe housing inner surface.

Therefore, in the gas generator shown in this embodiment, since theinclining end surface 351 of the filter means are pressed to theinclining surface 452 of the inner surface of the housing, it ispossible to prevent the short pass of the actuation gas in the endsurface of the filter means 355 without disposing a special member forsupporting the filter means 355.

In this gas generator also, a known gas generating agent 409, transfercharge 418, igniter 411 and the like can be used.

Embodiment of Self-contracting Type Filter 3

FIG. 24 shows a gas generator for an air bag of the present invention ofanother embodiment. The gas generator shown in FIG. 24, like the gasgenerator shown in FIG. 23, an inner surface of a housing 503 is formedwith inclining surfaces 552 a, b, and inclining end surfaces 551 a, bprovided on an end surface of the filter means 550 are supported by theinclining surfaces 552 a, b.

Unlike the gas generator shown in Embodiment 2, the gas generator shownin the present embodiment uses the filter means 550 which is provided atits axially end surfaces with inclining end surfaces 551. The incliningsurfaces 551 formed on the opposite sides of the axial end surfaces ofthe filter means are inclined so as to be narrowed radially outward, theupper end surface 551 a is inclined so as to descend outwardly in theradial direction, and the lower end surface 551 b is inclined so as toascend outwardly in the radial direction. A lower portion of the filtermeans of the present embodiment is formed so as to expand radiallyoutward.

The inclining surfaces 552 a, b capable of supporting the filter means550 are formed on an inner surface of the housing 503 so as to beopposed to the inclining end surfaces 551 a, b of the filter means.Especially in this embodiment, since the filter means is provided at itsopposite sides of axial end surfaces with inclining end surfaces 551,the inclining surfaces 552 a, b opposed to the inclining end surfaces551 a, b of the filter means 550 are formed on both the inner surface ofthe diffuser shell 501 and the inner surface of the closure shell 502.More specifically, the diffuser shell 501 and the closure shell 502 areformed by press-molding using various metal plates as in Embodiment 2,and the inclining portions 553 are formed on the shell on the side ofwhich the inclining surfaces of the filter means 550 are provided, i.e.,the diffuser shell 501 and the closure shell 502 in this embodiment. InFIG. 24, the inclining portions 553 a, b are formed between a circularportion 561 and a peripheral wall 562 in the diffuser shell 501, andbetween an annular portion 565 and a peripheral wall 566 in the closureshell 502.

Both the upper and lower end surfaces of the filter means 550 are formedinto the inclining end surfaces 551. The filter means 550 is disposed inthe housing so that the upper end inclining end surface 551 a is opposedto the inclining surface 552 a of the inner surface of the diffusershell 501, and the lower end inclining end surface 551 b is opposed tothe inclining surface 552 of the closure shell. An expanding portion 556of a lower portion of the filter means expanding in the radial directionis disposed so that the outer periphery of the expanding portion abutsagainst the inner surface of a peripheral wall 566 of the closure shell.

According to the gas generator of the present embodiment formed in thismanner, when the transfer charge 518 is ignited and burnt by theactuation of the igniter 511, the flame is ejected into the combustionchamber 505 from the through-hole 520 of the inner member 504, therebyigniting and burning the gas generating agent 509. The actuation gasgenerated by combustion of the gas generating agent 509 is purified andcooled while the gas passes through the filter means 550, and the gasbreaks the seal tape 522 and is discharged from the gas discharge port510. The filter means 550 is expanded radially due to passage of theactuation gas, and the inclining surfaces 551 a, b provided on the upperand lower ends of the filter means 550 abut against the incliningsurfaces 552 a, b provided on the inner surfaces of both the shells, andit is possible to prevent the short pass of the actuation gas betweenthe end surface of the filter means 550 and the inner surface of thehousing 503.

Especially in the gas generator shown in FIG. 24, the outer periphery ofthe expanding portion of the lower portion of the filter means 550 is incontact with the inner surface of the peripheral wall 566 of thehousing. Therefore, when the filter means 550 is expanded due to passageof the actuation gas, a portion thereof comes into contact with theinner surface of the peripheral wall of the housing, and it is possibleto suppress further deformation and control the expanding amount. Withthis arrangement, it is possible to stably secure the contact statebetween the filter means 550 and the inclining surface 552.

In relation with the present embodiment, the gas generator in which theupper and lower inner surfaces of the housing are provided withinclining surfaces which incline so as to be narrowed in the radialdirection can employ a structure shown in FIG. 25.

In addition to the internal structure such as layout and the number ofcombustion chambers and the igniters, the gas generator shown in FIG. 25is different from the one shown in FIG. 24 in that a diffuser shell 601and a closure shell 602 are joined by friction welding, and filter means(FIG. 20) which is not provided at its lower portion with an expandingportion is used as filter means 650. FIG. 26 is a schematic plan view ofthe gas generator for an air bag shown in FIG. 25.

In the gas generator of this embodiment, the diffuser shell 601 having agas discharge port 610 and the closure shell 602 having a flange portion667 are joined to each other by friction welding, thereby forming ahousing 603. A cylindrical inner shell 625 whose upper opening is closedis disposed in the housing 603 eccentrically with respect to the centeraxis of the housing. The outside of the inner shell 625 is defined as afirst combustion chamber 605 a, and the inside of the shell 625 isdefined as a second combustion chamber 605 b. Electrical ignition typeigniters 611 to be actuated by an electric signal and gas generatingagents 609 a, b which are to be ignited and burnt by actuation of theigniters are accommodated in the combustion chambers 605 a, b,respectively. Especially, as shown in FIG. 26, the igniter 611 a in thefirst combustion chamber 605 a is disposed inside of the innercylindrical member 604 in which a flame-transferring hole 619 isprovided eccentrically with respect to the peripheral wall. A transfercharge 618 which is to be ignited and burnt by the igniter 611 a isdisposed above the igniter 611 a. Although the transfer charge is notdisposed in the second combustion chamber 605 b in the drawing, it canbe disposed if required.

The inner shell 625 defines the first combustion chamber 605 a and thesecond combustion chamber 605 b, and a peripheral wall thereof providedwith an opening portion 660. The opening portion is closed by a sealtape 662 or the like. The seal tape 622 or the like for closing theopening portion 660 is formed so as to be burst, peeled, burnt ordetached by combustion of the second gas generating agent 609 baccommodated in the second combustion chamber 605 b. The opening portion660 is formed so that it does not open by combustion of the gasgenerating agent 609 a in the first combustion chamber 605 a.

In the gas generator shown in FIG. 25, the housing 603 is formed byjoining the diffuser shell 601 and the closure shell 602 by the frictionwelding. The diffuser shell 601 is formed with an inclining portion 653a which is inclined so as to be narrowed toward the ceiling surface 661from the peripheral wall 662. The closure shell 602 is also formed withan inclining portion 653 b which is inclined so as to be narrowed towardthe bottom surface 665 from the peripheral wall 666. The inner surfacesof the inclining portions 653 a, b of both the shells are the incliningsurfaces 652 which is opposed to inclining end surfaces 651 of thefilter means 650, and these inclining surface 652 functions as asupporting portion of the filter means 650. In the drawing, theinclining portions 653 a, b are formed by bending the shells, but it isalso possible to form the inclining portions by curving the shells.

Filter means 350 as shown in FIG. 20 whose upper and lower ends areformed with inclining end surfaces 651 is disposed in the housing 603.In the drawing, the filter means 350 is disposed so that its upperinclining end surface 351 is opposed to the inclining surface 652 a ofthe diffuser shell, and its lower inclining end surface 351 is opposedto the inclining surface 652 b of the closure shell 602.

In this gas generator, when the first igniter 611 a is actuated, thefirst transfer charge 618 is ignited and burnt. The flame of thetransfer charge 618 is discharged in the direction shown with the arrowin FIG. 26 so that the flame surrounds the inner shell 625 from theflame-transferring hole 619 provided eccentrically with respect to theinner cylindrical member 604. The flame discharged from theflame-transferring hole 619 ignites and burns the gas generating agent609 a in the first combustion chamber 605 a. The second igniter 611 b isactuated simultaneously with or slightly later than the first igniter611 a. The second gas generating agent 609 b in the second combustionchamber 605 b is ignited and burnt by the actuation of the igniter 611b, thereby generating the actuation gas. The opening portion 620provided in the peripheral wall of the inner shell 625 is opened due tothe pressure of the actuation gas. With this opening, the actuation gasgenerated by combustion of the second gas generating agent 609 b flowsinto the first combustion chamber 605 a.

The actuation gas generated by combustion of the first gas generatingagent 609 a and the second gas generating agent 609 b is purified andcooled while the gas passes through the filter means 350, and the gasbreaks the seal tape 622 and is discharged from the gas discharge port610. In the gas generator shown in this drawing also, the filter means350 expands radially outward by passage of the actuation gas, theinclining end surfaces 351 formed on the upper and lower end surfacesare pressed to the inclining surfaces 652 a, b in the housing, i.e., thesupporting portion, and it is possible to prevent the short pass of theactuation gas between the end surface of the filter means 350 and theinner surface of the housing 603.

Embodiment of Self-contracting Type Filter 4

FIG. 27 is a vertical cross sectional view showing another embodiment ofthe gas generator using filter means of the present invention. The gasgenerator shown in this embodiment is longer in the axial direction thanthe inner diameter thereof.

In the gas generator shown in FIG. 27, a filter means accommodatingcontainer 702 (hereinafter referred to “a filter container”) in whichfilter means 750 is accommodated is connected to axially one end opening730 of a cylindrical member 701, thereby forming a housing 703. Theother end opening 731 is closed by an annular member 732 in which anignition means container 704.

In the housing, a gas generating agent 709 which is to burnt to generatethe actuation gas is accommodated in the cylindrical member 701. Theinterior space of the cylindrical member 701 functions as the combustionchamber 705 in which the gas generating agent burns. A circular porousplate 733 spreading in the diametrical direction is disposed on the endon the side of the filter container 702 in the combustion chamber 705.The gas generating agent 709 in the combustion chamber 705 is supportedby the porous plate 733.

The igniting means container 704 fitted in the annular member 732 closesan end surface projecting into the combustion chamber 705. An ignitionmeans accommodating chamber 708 separated from the combustion chamber705 is provided inside the end surface. The ignition means comprising anigniter 711 and a transfer charge 718 is accommodated in the ignitionmeans accommodating chamber 708. A plurality of flame-transferring holes719 are formed in the peripheral wall of the ignition means container704, and the flame generated by actuation of the ignition means isejected from the flame-transferring holes 719 into the combustionchamber 705, thereby igniting and burning the gas generating agent 709.

The filter container 702 is substantially cylindrical shape as a whole,and peripheral edges of axially opposite end surfaces thereof are formedwith inclining portions 753 which is formed like the chamfering shapeand inclined so as to be narrowed in the axial direction of thecontainer. A through-hole 734 is formed in the end surface of the filtercontainer 702 on the side of the housing, and the other end surface isprovided with a stud bolt 735 for mounting the gas generator to themodule. A plurality of gas discharge ports 710 are formed in theperipheral wall. The interior space of the filter container 702 is incommunication with the combustion chamber 705 through the through-hole734 formed in the end surface of the housing. In the drawing, the filtercontainer 702 is formed by closing the opened end of the cup-like membercomprising a peripheral wall surface 736, an inclining portion 753 and ahousing side end surface 737 by a lid member comprising an incliningportion 753 and an end surface 739 including the stud bolt 735.

The filter means 350 of the present invention shown in FIG. 20., i.e., afilter means which is substantially cylindrical shape as a whole and theinclining end surfaces 351 which is inclined so as to be narrowed in theaxial extending direction are formed on axially opposite end surfacesthereof is accommodated in the filter container 702. The filter means350 is disposed so that its inclining end surface 351 is opposed to theinner surface of the inclining portion 753 of the filter container 702,i.e., the inclining surface 752. A gap 741 having a predetermined widthis secured between the outer peripheral surface of the filter means andthe inner wall surface of the filter container 702.

At the time of actuation of this gas generator, when the igniter 711 isactuated, the transfer charge 718 is ignited and burnt, and the flamethereof is ejected from the flame-transferring hole 719 of the ignitionmeans container 704 into the combustion chamber 705. The gas generatingagent 709 is ignited and burnt by the flame of the transfer charge 718ejected into the combustion chamber, thereby generating the actuationgas. The actuation gas flows into the filter container 702, and ispurified and cooled while the gas passes through the filter means 350,and discharged from the gas discharge port 710. With passage of theactuation gas through the filter means 350, the filter-means 350 expandsin the diametric direction, its inclining end surface 351 abuts againstthe supporting portion (i.e., the inclining surface 752) on the innersurface of the inclining portion 753 of the filter container 702, andcontracted in the axial direction. As a result, the filter means 350 isstrongly pressed to the inner surface of the filter container 702, andit is possible to prevent the short pass of the actuation gas passingbetween both the members. A gas generator having a plurality of igniters

Further, the present invention includes a gas generator for an air bag,comprising a housing with a plurality of gas discharge ports which formsan outer shell container and accommodates two or more ignition means toignite on an impact and a gas generating means which are to beindependently ignited and burnt by the ignition means so as to generatea combustion gas for inflating an air bag, wherein the gas dischargeports are closed by sealing means for maintaining an internal pressureof the housing to the given pressure, and by controlling the gasdischarge ports and/or the sealing means, a breaking pressure forbreaking the sealing means is adjusted at multiple stages and thereby adifference of the housing maximum internal pressures at the time wheneach ignition means is activated can be suppressed.

FIG. 32 is a vertical cross sectional view which shows a gas generatorfor an air bag according to the other embodiment of the presentinvention. The gas generator shown in this embodiment also has astructure being particularly suitable for being arranged in a driverside.

In particular, the gas generator shown in this embodiment ischaracterized by an arrangement of two combustion chambers provided inthe housing and a forming method.

Also in the present embodiment, a gas discharge port 1210 formed in adiffuser shell 1201 has two kinds of gas discharge ports 1210 a and 1210b having different diameters, and these are closed by a seal tape 1229for protecting a gas generating agent 1252 from an influence of anenvironment such as a humidity outside the housing. By providing twokinds of gas discharge ports 1210 a and 1210 b having different innerdiameters (and opening areas), a combustion internal pressure in thehousing 1203 at an actuation can be equalized (stabilizing of acombustion performance).

That is, in the gas generator shown in this embodiment, in a cylindricalhousing 1203 obtained by joining a diffuser shell 1201 having aplurality of gas discharge ports 1210 and a closure shell 1202 forforming an inner storing space together with the diffuser shell 1201 andapplying a friction welding to these shells, a cylindrical inner shell1204 in a capsule-like shape having a circle in the horizontal crosssection and a closed upper end is arranged and fixed eccentrically withrespect to the center axis of the housing, thereby forming a firstcombustion chamber 1250 is formed in an outer side thereof and forming asecond combustion chamber 1260 in an inner side thereof.

A eccentric degree of the inner shell 1204 arranged in the housing 1203with respect to the housing 1203 can be suitably changed according to adesired volume ratio of a combustion chamber and the like, and may bechanged according to a structure inside the housing 1203, for example,whether or not a coolant/filter 1225 exists. As an example, like the gasgenerator shown in this drawing, when the coolant/filter 1225 isarranged opposite to a peripheral wall surface of the housing 1203, itis possible to suitably select the eccentric degree in a range between10 and 75%. However, since this range can be changed due to a size ofthe igniters 1251 and 1261 and the like, the range is only a measure ofeccentricity of the inner shell 1204 in the gas generator shown in FIG.32.

The inner shell 1204 may be formed in various kinds of shapes such as arectangular shape, an oval shape and the like in a horizontal crosssection, in order to join easily to the closure shell 1202, etc., it ispreferable to be formed in a circular shape. In other wards, thehorizontal cross sectional shape of the inner shell 1204 has to be acircular shape when joining the inner shell 1204 and the closure shell1202 by a friction welding, and also when joining by a laser welding, itis necessary to keep an emitting distance of the laser constant.

As mentioned above, in this embodiment, the first combustion chamber1250 and the second combustion chamber 1260 are defined by the innershell 1204. That is, the first combustion chamber 1250 is provided onthe outer side of the inner shell 1204, and the second combustionchamber 1260 is provided on the inner side of the inner shell 1204. Avolume ratio between the first combustion chamber 1250 and the secondcombustion chamber 1260 (a volume of the first combustion chamber:avolume of the second combustion chamber) is set to 3.3:1 in the presentembodiment, and it can also be suitably selected in a range of 97:1 to1:1.1. However, also with respect to the volume ratio, the selectedrange can be suitably changed due to a size of the igniters (1251, 1261)and a shape of the gas generating agents (1252, 1262). Accordingly, theabove range shows a range which can be selected in the structure of thegas generator shown in this drawing.

As mentioned above, the gas generating agents (1252, 1262) arerespectively stored in the second combustion chamber 1260 and the firstcombustion chamber 1250 which are partitioned by the inner shell 1204.The first gas generating agent 1252 is stored in the first combustionchamber 1250 and the second gas generating agent 1262 is stored in thesecond combustion chamber 1260, respectively. In the present embodiment,the first gas generating agent 1252 and the second gas generating agent1262 have the same shape or the like. The gas generating agentsdifferent from each other in at least one of a burning rate, acomposition, a composition ratio and an amount can be stored in therespective combustion chambers.

The inner shell 1204 which defines the first combustion chamber 1250 andthe second combustion chamber 1260 is arranged eccentrically withrespect to the center axis of the housing 1203, and the secondcombustion chamber 1260 provided inside the inner shell 1204 iseccentric with respect to the housing 1203. The igniters arerespectively arranged in the first combustion chamber 1250 and thesecond combustion chamber 1260, the second igniter 1261 arranged in thesecond combustion chamber 1260 is disposed in the center of the secondcombustion chamber 1260 which is eccentric with respect to the centeraxis of the housing 1203. Therefore, a flame generated by an activationof the igniter 1261 can uniformly burns the second gas generating agent1262. And the second igniter 1261 and the first igniter 1251 disposed inthe first combustion chamber 1250 are both arranged eccentrically withrespect to the center axis of the housing 1203. As mentioned above, byarranging eccentrically the first and second igniters as well as theinner shell 1204 with respect to the center axis of the housing 1203, arange of a difference in the volume ratio of the first and secondcombustion chambers can be made larger, and the size of the housing 1203in a diametrical direction can be restricted as much as possible.

Among the igniters arranged in the respective combustion chambers, theigniter 1251 arranged in the first combustion chamber 1250 has atransfer charge 1208 arranged in a peripheral and upper directionsthereof. For convenience at assembling the gas generator, or in order toprevent the transfer charge 1208 from being scattered in the firstcombustion chamber 1250 due to the impact and the vibration applied atmounting on the vehicle, and to prevent an ignition performance to thefirst gas generating agent 1252 form being slipped, the transfer charge1208 is stored in a transfer charge container 1226. The transfer chargecontainer 1226 is easily broken due to the combustion of the transfercharge 1208 arranged therein and formed by an aluminum having athickness (for example, about 200 μm) so as to transfer the flame to theperiphery thereof. On the other hand, a transfer charge like the onearranged in the first combustion chamber 1250 is not necessarilyrequired in the second combustion chamber 1260. This is because thesecond gas generating agent 1262 is ignited more easily, than the firstgas generating agent 1252, and the pressure of the second combustionchamber is increasing in a sealed state until the breaking member 1207for sealing a hole 1206 of the below-described inner shell 1204 isruptured. The breaking member 1207 is not ruptured even when theinternal pressure of the combustion chamber 1250 increases due to thecombustion of the first gas generating agent 1252 but it is rupturedwhen the internal pressure of the second combustion chamber 1260increases more than that of the first combustion chamber 1250. However,the transfer charge can be used as required.

A cylindrical member 1236 is placed in the first combustion chamber 1250so as to surround an outer side in the radial direction of the firstigniter 1251 and the transfer charge 1208 disposed above the igniter.The cylindrical member 1236 is formed into a cylindrical shape open atboth upper and lower ends, one end portion thereof is outwardly fittedto an outer periphery of a portion fixed with the igniter 1251 so thatno gap is formed. And the other end portion is inserted to be supportedby a retainer 1211 disposed near an inner surface of a ceiling portionof the diffuser shell 1201 so as to be fixed to a predetermined portion.A plurality of flame-transferring holes 1237 are formed on a peripheralwall of the cylindrical member 1236, and the flame generated by thecombustion of the transfer charge 1208 is injected from theflame-transferring hole 1237 so as to ignite and burn the first gasgenerating agent 1252 disposed in the outer side of the cylindricalmember. It is preferable that the cylindrical member 1236 is made of thesame material as that of the housing 1203.

In particular, in the gas generator shown in this embodiment, the firstcombustion chamber 1250 is formed into an annular shape similar to acrescent shape obtained by stamping an inner side of a circle roundly,as shown in a perspective plan view in FIG. 33, and the first gasgenerating agent 1252 is placed therein. Accordingly, in the firstcombustion chamber 1250, as is different from the second combustionchamber 1260, a distance between the gas generating agent 1252 and theigniter 1251 is varied with a place for storing the gas generating agent1252. Therefore, at a time of ignition of the igniter 1251, the ignitionand the combustion of the first gas generating agent 1252 are performedunevenly. Then, the flame-transferring hole 1237 provided in aperipheral wall of the inner cylindrical member 1236 restricts adirection thereof so as to lead the flame of the transfer charge 1208 ina direction shown by an arrow in FIG. 33. Accordingly, it is possible toburn the gas generating agent 1252 in a portion shaded by the secondcombustion chamber 1260 (i.e. the inner shell 1204) evenly. Further, inplace of the inner cylindrical member 1236, a injecting-directionrestricting means (not shown) having holes formed in a direction shownby an arrow in FIG. 33 can be used. The injecting-direction restrictingmeans restricts the direction of the injecting flame which is generatedby the activation of the first ignition means (the igniter 1251 and thetransfer charge 1208 in FIG. 32) for igniting the first gas generatingagent 1252, in order to effectively burn the first gas generating agent1252. As the injecting-direction restricting means, for example, acup-like container having one end portion closed by a cylinder memberand in which a nozzle for leading the flame of the ignition means in adesired direction (a direction shown by an arrow in FIG. 33) is providedon a peripheral wall portion. In this case, the injecting-directionrestricting means is used in a state of being mounted (covered) aroundthe first ignition means. Also in the case of using the aboveinjecting-direction restricting means, it is preferable that the firstignition means arranged inside it comprises the igniter and the transfercharge which is to be ignited and burnt by the activation of theigniter.

The inner shell 1204 which defines the first combustion chamber 1250 andthe second combustion chamber 1260 is formed into a capsule shape asmentioned above, and a plurality of opening portions 1205 are formed ona peripheral wall thereof. The opening portion 1205 is designed such asto be opened only by the combustion of the second gas generating agent1262 stored in the second combustion chamber 1260 and is not opened bythe combustion of the first gas generating agent 1252 stored in thefirst combustion chamber 1250. In the present embodiment, the openingportion 1205 comprises a plurality of holes 1206 provided on theperipheral wall of the inner shell 1204 and the breaking member 1207 forclosing the hole, and a stainless seal tape is used as the breakingmember 1207. The breaking member 1207 is designed such as to be broken,peeled, burnt or removed only by the combustion of the second gasgenerating agent 1262 so as to open the hole 1206 but not to be brokenby the combustion of the first gas generating agent 1252.

The above inner shell 1204 is fixed by connecting an open lower portion1213 thereof to the closure shell 1202. When the closure shell 1202comprises the collar portion 1202 a for fixing the igniter, the innershell 1204 can be mounted to the collar portion 1202 a. In the gasgenerator shown in FIG. 32, the closure shell 1202 is formed such as tointegrally joint a circular collar portion having a size capable offixing two igniters on a bottom surface of the cylindrical shell portion1202 b jointed to the diffuser shell 1201, and the inner shell 1204 isjointed to the collar portion 1202 a. The collar portion 1202 a can beintegrally formed on the bottom surface of the cylindrical shell portion1202 b in a circular shape capable of being fixed at each igniter, andcan be integrally formed on the bottom surface of the cylindrical shellportion 1202 b. In such a case, the inner shell 1204 can be directlymounted on the bottom surface of the cylindrical shell portion 1202 b inaddition to the collar portion 1202 a of the closure shell.

In the present embodiment, a joint of the inner shell 1204 and theclosure shell 1202 can be performed by an convex-concave joint inaddition to a friction welding, a cramping, a resistance welding and thelike. In particular, in the case of joining the both by frictionwelding, preferably, it is performed in a state of fixing the closureshell 1202. Accordingly, even when the axial cores of the inner shell1204 and the closure shell 1202 are not aligned to each other, afriction welding can be performed stably. In other words, when frictionwelding is performed in a state of fixing the inner shell 1204 androtating the closure shell 1202, a center of gravity of the closureshell 1202 is shifted from a center of rotation and thereby a stablefriction welding cannot be performed. Therefore, in the presentinvention, friction welding is performed in a state of fixing theclosure shell 1202 and rotating the inner shell 1204. Further, atfriction welding, it is preferable that the closure shell 1202 ispositioned and fixed so as to always mount the inner shell 1204 to adetermined position. Accordingly, it is preferable that a positioningmeans is suitably provided in the closure shell 1202. A gas generatingagent fixing member 1214 is arranged in the inner shell 1204 in order tosafely and smoothly perform a connection to the closure shell 1202. Thegas generating agent fixing member 1214 is used in order to prevent thegas generating agent 1262 from directly contacting with the inner shell1204 at a time of friction welding the inner shell 1204 to the closureshell 1202 and to obtain a placing space for the igniter 1261 inside thespace formed by the inner shell 1204. When mounting the inner shell 1204to the closure shell 1202, in addition to the above friction welding, itis possible to mount by an convex-concave joint as well as a crimping, aresistance welding and the like. Also in this case, an assemblyperformance is improved by using the gas generating agent fixing member1214. The gas generating agent fixing member 1214 adopts here a canistermade of aluminum and having a thickness which can be easily broken bythe combustion of the gas generating agent 1262, as one example, andfurther, a suitable member capable of achieving the object mentionedabove (regardless a material, shape and the like) such as a porousmember made of a wire mesh. Besides, when the above gas generating agentfixing member 1214 is not used, it is possible to form a lump of the gasgenerating agent obtained by forming a lump of the single-holecylindrical gas generating agent 1262 into the same shape as the innerspace of the inner shell 1204 and place it in the inner shell 1204. Inthis case, the gas generating agent fixing member 1214 may be omitted.

In the present embodiment, the collar portion 1202 a of the closureshell 1202 is formed in a size capable of fixing two igniters 1251 and1261 horizontally. Accordingly, two igniters 1251 and 1261 arepreviously fixed to the collar portion 1202 a by crimping, etc., andthen, this collar portion 1202 is integrally formed with the cylindricalshell portion 1202 b so as to form the closure shell 1202, and thereby,two igniters 1251 and 1261 can be fixed to the closure shell 1202. Inthe drawing, the first igniter 1251 and the second igniter 1261 aredescribed in the same size, however, they may be structured such as tohave a different output at each combustion chamber. Further, in thisembodiment, a cable 1215 connected to each igniter 1251 and 1261 so asto transmit an activating signal is drawn out in the same direction.

A coolant/filter 1225 is arranged in the housing 1203 as filter meansfor purifying and cooling the combustion gas generated by the combustionof the gas generating agent. The gases generated by the combustion ofthe first and second gas generating agents both pass through thecoolant/filter 1225. In order to prevent a short pass, that is, toprevent the combustion gas from passing between an end surface of thecoolant/filter 1225 and an inner surface of the ceiling portion of thediffuser shell 1201, the upper and lower inner peripheral surfaces ofthe coolant/filter 1225 and the inner surface of the housing may becovered with a cylindrical short-pass preventing member having an inwardflange. In particular, in the gas generator shown in FIG. 32, aself-contracting type coolant/filter 1225 tapers at both upper and lowerends outwardly in the radial direction. A gap 1228 which is a flow pathfor the combustion gas is formed on the outer side the coolant/filter1225.

For example, in the gas generator shown in FIG. 32, the igniter (1251,1261) and the inner shell 1204 are arranged eccentrically with respectto the housing 1203. In the above gas generator, when the diffuser shell1201 and the closure shell 1202 are joined by friction welding, joiningthe both the shells can be performed stably by fixing the side of theclosure shell 1202 at the time of friction welding. Particularly, wheninner shell 1204 is directly mounted to the closure shell 1202 byfriction welding, as shown in FIG. 32, it is preferable that a flangeportion 1232 for mounting the gas generator to the module case isprovided in the side of the closure shell 1202, and a positioningportion is formed in a portion constituting the flange portion 1232, forexample, a protruding portion 1233 or the like by notching theperipheral edge thereof. In case of forming in this manner, since theclosure shell 1202 is always fixed in a definite direction on thepositioning portion, the inner shell 1204 can be securely mounted at adetermined position.

In the gas generator formed in the above manner, when the first igniter1251 arranged in the first combustion chamber 1250 provided on the outerside the inner shell 1204 is activated, the first gas generating agent1252 in the combustion chamber 1250 is ignited and burnt so as togenerate the combustion gas. And a little gap is obtained between theinner shell 1204 and the coolant/filter 1225 and this gap allows a gasflow between the coolant/filter 1225 and the inner shell 1204, andthereby, the combustion gas can effectively use all the surface of thefilter 1225. The combustion gas is purified and cooled while passingthrough the coolant/filter 1225, and thereafter is discharged from thegas discharge port 1210.

On the other hand, when the second igniter 1261 arranged in the innershell 1204 is activated, the second gas generating agent 1262 is ignitedand burnt so as to generate the combustion gas. The combustion gas opensthe opening portion 1205 of the inner shell 1204 and flows into thefirst combustion chamber 1250 from the opening portion 1205. Thereafter,it passes through the coolant/filter 1225 as the combustion gas of thefirst gas generating agent 1252 does, and is discharged from the gasdischarge port 1210. The seal tape 1229 which closes the gas dischargeport 1210 is ruptured by passage of the combustion gas generated in thehousing 1203. The second gas generating agent 1262 is ignited and burntdue to the activated second igniter 1261, and is never directly burnt onthe combustion of the first gas generating agent 1252. This is becausethe opening portion 1205 of the inner shell 1204 is opened only by thecombustion of the second gas generating agent 1262 but is not opened bythe combustion of the first gas generating agent 1252.

In the gas generator formed in the above manner, the ignition timings oftwo igniters is adjusted such as to activate the second igniter 1261after activating the first igniter 1251, or to simultaneously activatethe first igniter 1251 and the second igniter 1261, and thereby anoutput's forms (an operating performance) of the gas generator can beoptionally adjusted so that, under various conditions such as a vehiclespeed at a time of collision, an environmental temperature, inflation ofthe air bag can be made most suitable in the air bag apparatus mentionedbelow. Particularly, in the gas generator shown in FIG. 32, twocombustion chambers are arranged in the radial direction, by whereby aheight of the gas generator can be restricted as much as possible.

Also in the gas generator shown in this drawing, a plurality of gasdischarge ports 1210 formed in the housing 1203 are structured such thatthe opening diameter and/or the opening area thereof are controlled intwo or more kinds. Therefore, a difference of the housing maximuminternal pressure at the time when each ignition means is activated issuppressed, the internal pressure at the time when the gas generator isactuated is equalized, which provides a gas generator for an air baghaving a stable combustion performance. Further, also in the gasgenerator according to this embodiment, by setting the opening area ofeach gas discharge port 1210 constant but by changing the thickness ofthe sealing means 1229 such as a seal tape so as to adjust the breakingpressure, a difference of the housing maximum internal pressure at thetime when each ignition means is activated can be suppressed. Further,it is naturally possible to control both of the opening diameter and/orthe opening surface in the gas discharge port 410 and the thickness ofthe sealing means 1229.

What is claimed is:
 1. A multistage type air bag apparatus, comprising:a multistage gas generator for an air bag including, in a housing, afirst igniter and a second igniter, selectively initiated by activationsignals, provided adjacent to one another; a first lead wire having afirst connector, provided on a first end thereof, for selectivelyconnecting the first lead wire to the first igniter, the first lead wireextending from a side peripheral portion of the first connecter suchthat when the first connector is attached to the first igniter, thefirst lead wire extends only in a predetermined direction on animaginary plane substantially perpendicular to a central axis of thehousing without bending the first lead wire; and a second lead wirehaving a second connector, provided on a first end thereof, forselectively connecting the second lead wire to the second igniter, thesecond lead wire extending from a side peripheral portion of the secondconnector such that when the second connector is attached to the secondigniter, the second lead wire extends only in the predetermineddirection and only on the imaginary plane without bending the secondlead wire.
 2. A multistage type air bag apparatus according to claim 1,wherein at least one of the first connector and the second connector hasdefining means that specifies a unique connection with corresponding oneof the first igniter and the second igniter.
 3. A multistage type airbag apparatus according to claim 2, wherein the defining means is formedon a way-connector provided at least one position on the lead wire whichconnects the igniter and an outputting portion that outputs anactivation signal for activating at least one of the first igniter andthe second igniter.
 4. A multistage type air bag apparatus according toclaim 2, wherein the first igniter includes a connecting portion forattaching the first connector thereto, and the defining means is formedon the connecting portion of the first igniter and on the firstconnector.
 5. A multistage type air bag apparatus according to claim 1,further comprising: a control unit including a first outputting portionfor selectively outputting an activation signal to the first igniter,wherein the first lead wire has a third connector, at a second endthereof, selectively attached to the first outputting portion, andwherein the first outputting portion and the third connector includedefining means that specifies a unique connection therebetween.
 6. Amultistage type air bag apparatus according to claim 4, wherein thefirst connector and a connecting portion include a conducting portionfor conducting an activation signal, and wherein the defining means isrealized by changing at least one of a shape, number, and position ofthe conducting portion.
 7. A multistage type air bag apparatus accordingto claim 2, wherein the defining means is realized by changing at leastone of a shape, number and position of a conducting portion, forconducting an activation signal, provided on the at least one of thefirst connector and the second connector.
 8. A multistage type air bagapparatus according to claim 1, wherein the first connector and thesecond connector are made of a single connector element, and the singleconnector element is provided with defining means that specifies aunique connection with the first igniter and the second igniter.
 9. Amultistage type air bag apparatus according to claim 1, wherein thefirst connector and the second connector are connected to each other bya plastic member.
 10. A multistage gas generator for an air bag,comprising: a housing including a gas discharge port; a first igniterattached to said housing and selectively initiated by activationsignals, said first igniter selectively receiving a first connectorprovided at one end of a first lead wire, the first lead wire extendingfrom a side peripheral portion of the first connector such that when thefirst connector is attached to the first igniter, the first lead wireextends only in a predetermined direction on an imaginary planesubstantially perpendicular to a central axis of the housing withoutbending the first lead wire; and a second igniter attached to saidhousing and selectively initiated by the activation signals, said secondigniter being adapted to receive a second connector provided at one endof a second lead wire, the second lead wire extending from a sideperipheral portion of the second connector such that when the secondconnector is attached to the second igniter, the second lead wireextends only in the predetermined direction and only on the imaginaryplane without bending the second lead wire.
 11. A multistage gasgenerator for an air bag according to claim 10, wherein the firstigniter includes first defining means that only allows connection of thefirst connector, and the second igniter includes second defining meansthat only allows connection of the second connector, wherein the firstdefining means and the second defining means are different from oneanother in terms of at least one of a shape, number, and position.
 12. Amultistage gas generator for an air bag according claim 11, wherein thefirst defining means is one of a groove and a projection formed in thefirst igniter and other of the groove and the projection formed in theconnector.
 13. A method of connecting lead wires to igniters attached tomultistage type air bag gas generator, comprising: providing the gasgenerator with a first igniter; providing the gas generator with asecond igniter; providing a first lead wire having a first connector,provided on a first end thereof, for selectively connecting the firstlead wire to the first igniter, the first lead wire extending from aside peripheral portion of the first connecter such that when the firstconnector is attached to the first igniter, the first lead wire ispermitted to extend only in a predetermined direction on an imaginaryplane substantially perpendicular to a central axis of a gas generatorhousing without bending the first lead wire; and providing a second leadwire having a second connector, provided on a first end thereof, forselectively connecting the second lead wire to the second igniter, thesecond lead wire extending from a side peripheral portion of the secondconnecter such that when the second connector is attached to the secondigniter, the second lead wire is permitted to extend only in thepredetermined direction and only on the imaginary plane without bendingthe second lead wire.
 14. The method of claim 13, further comprising:providing the first igniter and the first connector with first definingmeans that specifies a first unique connection between the first igniterand the first connector; and providing the second igniter and the secondconnector with second defining means that specifies-a second uniqueconnection. between the second igniter and the second connector, thesecond unique connection being different from the first uniqueconnection in terms of at least one of a shape, number and positionthereof.
 15. A method of connecting a connector according to claim 14,wherein the first defining means providing step includes, providing oneof a groove and a projection in the first igniter, and providing otherof the groove and the projection in the first connector.